ELEMENTARY GEOLOGY
ELEMENTARY
GEOLOGY
WITH SPECIAL REFERENCE
TO CANADA
BY
A. P. COLEMAN, M.A.,Ph.D.,F.R.S.
Professor of Geology, University of Toronto
AND
W. A. PARKS, B.A.,Ph.D.,F.R.S.C.
Professor of Paleontology, University of Toronto
MCMXXII
LONDON & TORONTO
J. M. DENT & SONS LTD.
All rights reserved
PRINTED IN GREAT BRITAIN
PREFACE
So many elementary text-books of Geology are available
that it seems almost superfluous to add to the number.
Geology, however, is a science embracing, not only general
principles of world-wide importance, but the application of
those principles to the working-out of the history of a given
locality or country.
In this work the general principles of geology are illus-
trated, as far as possible, by Canadian examples, and the
geology of Canada is given especial prominence in the section
devoted to Historical Geology.
This method of treatment introduces the student to the
subject by reference to localities and geological structures
with which he is familiar and lays a local foundation on
which the greater geological history of the whole world may
be built.
While the book is primarily intended as an introduction
to general geology, the emphasis laid on Canadian geological
history makes it suitable to those desiring an outline of the
geology of Canada. From this point of view, it is hoped that
the work will be acceptable to the general reader and to
persons engaged in the mining industry in Canada.
TORONTO, ONTARIO.
50 i it - 5
TABLE OF CONTENTS
PART L— PHYSICAL GEOLOGY
CHAPTER I
INTRODUCTORY
PAGE
GENERAL STATEMENT OF THE AIMS OF GEOLOGY . . . i
SUBDIVISIONS OF GEOLOGY ....... 2
THE EARTH AS A WHOLE ....... 3
THE EARTH'S MOTIONS. ... ..... 3
THE COMPOSITION OF THE EARTH ...... 4
CHAPTER II
MINERALS AND ROCKS
MINERALS . . . . . . ,, . . . 6
Physical properties of minerals . ;; ..' ... 7
Common minerals forming igneous rocks . . . . 9
Non-essential and secondary minerals of igneous rocks . 12
Additional minerals of the metamorphic rocks . . .13
Minerals of the sedimentary rocks . . . . . 15
Minerals used as ores of the metals . . . . .16
Other minerals of economic importance . . . .19
ROCKS . . . . . . . . .21
Igneous rocks '..•'..'., ... . . . . 22
Sedimentary rocks . .... . . . . 29
Metamorphic rocks . . . . . . . 33
CHAPTER III
DYNAMIC GEOLOGY
THE SOURCES OF GEOLOGICAL ENERGY . . . .36
HYPOGENE FORCES ........ 36
Condition of the earth's interior . . . . . 37
Secular changes of level . . . . . . . 39
Evidences of slow changes of level in recent times . . 40
Changes of level in mountain building .... 42
Depression of the sea bottom . . . . . .42
Isostasy. ......... 43
Epeirogenesis and orogenesis ...... 43
Diastrophism ........ 44
vii
viii ELEMENTARY GEOLOGY
HYPOGENE FORCES — continued PAGE
Causes of changes of level . . . . , . 44
Movements in the asthenosphere . . . . ' . 46
Earthquakes . . . . , . .* . . 47
Accompaniments of earthquakes . < . .-rfy.-. -, -. . 49
Distribution of earthquakes . .- .' ' il-.'- . . 50
Volcanoes . . . . . . . -50
Lava . . . ., '..,. » .., ,. ,. , . 51
Volcanic gases . . »'•' . '--. :s- * - . -. . . 52
Volcanoes with very fluid lavas . , . . . 52
Volcanoes with explosive eruptions . t . •. . , 53
Intermediate types of volcanoes . . • ., . . , 55
Calderas . . ... . .' . . 56
Submarine volcanoes . . . . . . . 57
Distribution of volcanoes .. . . ^.. . 58
Causes of volcanoes . . . .-" . . "*"' '. "-.•" . 58
Sources of the gases of volcanoes •. . . : . - , 60
Extinction of volcanoes . . . . • , v. . 61
Fumaroles and hot springs . . v. -. -. . .62
Geysers . . . . . '.. - . , . • :. . . 62
Metamorphism . . . . • . ' . ... . '63
Effects of metamorphism on sedimentary rocks . . * 64
EPICENE FORCES . . .. .. . . ... . 65
Weathering . . . . . . . . . . 65
Oxidation . . . . , . . . . . . 66
Carbon dioxide . . .. -, .. .. ,. . 66
Change of temperature . , . . . . . 67
Rain action . .. . . . . .-., . * .• - ^. 69
Ground water . . . . . . r '. . '., 70
Landslips ". . . . . . i • ' *' 71
Artesian waters . ' . . » . . . .72
Mineral springs . . . . . . . . 72
Caves . . " . . . ..;.-. 72
The work of running water . . ' . " . r . . 74
Watersheds and catchment basins . , . - . -. " .-.' 75
Transporting power of rivers . . . . " . . . 76
Types of work done by rivers . . . . .- . 76
Meanders . . . ..... . . 78
Deltas and estuaries . - . . ' . . . . 79
Features of youthful rivers •-. .. .. . : . '' . 80
Peneplanation .. - . . . , . * . 84
The work of seas and lakes . '. . . . . . 85
Destructive work of waves . . . . . . 85
Constructive work of waves .. * .. ;. . . 87
Ocean currents . , ..v. . ... . . 88
Tides . . ... . . ... . 90
The salts of the sea . . . . . „ . ..-.••.'•'. . 92
Deposits in salt lakes . . v.»; • 93
Marine deposits . . ,. , v • • 94
The work of snow and ice . .v •• . *.. •* . 95
Glaciers ^. • . . . . ••'>•'£*••'••?•• * ; . 96
Icebergs . . . . .. . i'-' »• • . 101
CONTENTS ix
EPICENE FORCES — continued PAGE
Drift deposits . '..''• ..'." . . . V . . 102
The atmosphere . . . . . ... 103
Work of the wind . ... . . . . 104
Life as a geological factor . . ...'"," . . . 106
Geological work of plants. Soils . . . . . 106
Protective work of plants . . • . ... .107
Rock formation by plants . . . . • . .107
Fossil fuels . . :. . ; . . .108
Geological work of animals . . .- . . .109
Foraminifers . . . . . '.'. . . 109
Corals . . no
Shellfish ..no
Vertebrates. ... . . . . . .in
CONFLICT OF FORCES IN THE WORLD . . . .112
GEOLOGICAL TIME. . . . . . ... 113
CHAPTER IV '
STRUCTURAL GEOLOGY
STRATA . . . . . . . . * '. 115
Joints . . . . . . . . 117
Concretions . . . . . . . . .118
Attitude of stratified rocks . . . . . . .119
Folds . . . . . . . . . .119
Zones of deformation and of fracture . . . . .121
Faults .......... 122
Normal faults ....... . 122
Reversed or thrust faults . . . . . .123
Discordances . . . . . . . . .125
STRUCTURE OF ERUPTIVE ROCKS . . . . .126
Superficial or volcanic structures . . . . ' '• 126
Amygdaloids . . . . . . . 127
Pillow or ellipsoidal structure . . . . .- . . 128
Structures caused by explosive eruptions . . . . 128
Underground structures . . . . i , .129
Dikes . . . ... . . . .129
Sheet-like forms and laccoliths . . . . . / . 129
Batholiths . . . . . . ... 130
Stocks or bosses . . . . . . , . 132
Joints of eruptive rocks '. . . , . . .132
Columns ..... *. . . . . 132
Joints of coarser -grained eruptives . . . . . 133
STRUCTURES OF SCHISTOSE ROCKS . '. . . . 134
Foliation . . . . Y . . . .134
Slaty cleavage . . . . . ~ . . .135
x ELEMENTARY GEOLOGY
PART II.— HISTORICAL GEOLOGY
CHAPTER I
THE MAKING OF THE WORLD
PAGE
GENERAL REMARKS . . . . . . .137
THE NEBULAR THEORY . ". . . . . .138
THE PLANETESIMAL THEORY . . . . . . .141
CHAPTER II
THE GENERAL PRINCIPLES OF HISTORICAL GEOLOGY
THE STUDY AND CORRELATION OF STRATA . . . .143
Superposition . . . ... . . .144
Unconformities . . . . . . . .144
Basal conglomerates . . . . . . .145
Lithological characters . . . . . . .146
Fossils .......... 146
THE SUBDIVISIONS OF GEOLOGICAL TIME . . . .150
Table of the main divisions of geological time . . .154
CHAPTER III
THE NOMENCLATURE AND CLASSIFICATION OF ORGANISMS
GENERAL PRINCIPLES OF NOMENCLATURE AND CLASSIFICATION . 155
TABLE SHOWING OUTLINE OF THE CLASSIFICATION OF ORGANISMS . 156
CHAPTER IV
THE ARCHAEAN OR PRE-CAMBRIAN
THE GRENVILLE SERIES . . . ... •' . . . 163
Distribution of the Grenville . . > ..' . . 165
Economic features of the Grenville . ... . .166
Attitude of the Grenville . . V » . .166
THE KEEWATIN SERIES. . . •. . . . .167
The Keewatin of the type locality -. . -. . . 167
The Keewatin series in other regions of Canada . . .168
The Keewatin series in other countries . -. . .169
THE COUTCHICHING SERIES . . . . . . .169
THE LAURENTIAN . . . . . . . .169
Other regions which may be Laurentian . . . . 171
THE POST-LAURENTIAN INTERVAL .... , . ..,' 171
THE SUDBURY OR TlMISKAMING SERIES . . . . . 172
GENERAL FEATURES OF THE EARLIER PRE-CAMBRIAN . .174
CONTENTS xi
PAGE
THE ALGOMAN OR POST-SUDBURIAN GRANITES . * .. • . 175
THE POST- ALGOMAN INTERVAL *"". ' V . ." . . 175
THE HURONIAN SERIES » • , . .*.•'. . 175
THE ANIMIKIE SERIES . . . . . . . .178
THE KEWEENAWAN SERIES . . . •'. ^ ; .. . 179
THE WESTERN PRE-CAMBRIAN . . . ..:... . 181
The Shuswap series ».,... . . -..>,•. . . 181
The Bel tian series .... •.» , - ...... • , . 182
CONDITIONS IN THE LATER PRE-CAMBRIAN 182
CHAPTER V
THE PALEOZOIC ERA— THE CAMBRIAN PERIOD
PHYSICAL EVENTS IN NORTH AMERICA DURING THE CAMBRIAN . 185
THE CAMBRIAN SYSTEM IN CANADA . . . . .187
THE LIFE OF THE CAMBRIAN. . . . . . .190
Cambrian fossils of the maritime provinces . . . 196
Fossils of the Potsdam sandstone . . . . . 196
Cambrian fossils of the Rocky Mountain region . . .198
CHAPTER VI
THE ORDOVICIAN PERIOD
PHYSICAL EVENTS OF THE ORDOVICIAN IN NORTH AMERICA . 199
THE ORDOVICIAN SYSTEM IN CANADA ..... 201
The sequence of Ordovician rocks in Ontario . . . 202
Economic products of Ordovician rocks . . . .204
LIFE OF THE ORDOVICIAN ....... 204
Ordovician plants . . . . . . . .204
Ordovician invertebrates . . . . . . .204
CHAPTER VII
THE SILURIAN PERIOD
PHYSICAL EVENTS OF THE SILURIAN IN NORTH AMERICA . 217
THE SILURIAN SYSTEM IN CANADA 218
The sequence of Silurian rocks in Ontario .
Economic products of Silurian rocks
Correlation of Silurian formations ....
Correlation table of the Silurian formations of Nova Scotia
Ontario, and England . " " ~f ~ ' V '^
218
220
222
222
LIFE OF THE SILURIAN •* »«"•; . ; . . . V . . 222
xii ELEMENTARY GEOLOGY
CHAPTER VIII
THE DEVONIAN PERIOD
PAGE
PHYSICAL EVENTS OF THE DEVONIAN IN NORTH AMERICA . 232
THE DEVONIAN SYSTEM IN CANADA . ^ K _ -,..,../.= 233
The sequence of Devonian rocks in Ontario : v-: . • ;»•- 235
LIFE OF THE DEVONIAN '. ". °. ". * '•'llV; /' i '""'• :" 0|. 238
Devonian plants % . . r«7 ^f'^J n^ -,- -JlTia^
Devonian invertebrates . . . . . . ,";. 239
Devonian vertebrates . . . . . . . 245
CHAPTER IX
THE CARBONIFEROUS PERIOD
CORRELATION TABLE OF THE CARBONIFEROUS AND PERMIAN OF
EUROPE AND NORTH AMERICA ...... 250
PHYSICAL EVENTS OF THE CARBONIFEROUS IN NORTH AMERICA . 251
COAL . . ...'.. • • ... ..- .252
THE CARBONIFEROUS SYSTEM IN CANADA ... . 254
Subdivisions of the Carboniferous rocks in eastern Canada . 254
The coal fields of Nova Scotia . ... 256
Carboniferous formations of the Southern Rockies . . 257
LIFE OF THE CARBONIFEROUS ... .. > * . . . 258
Carboniferous plants . ... . • •"" • 258
Carboniferous invertebrates . . . ; . .261
Carboniferous vertebrates ... . . . . .265
CHAPTER X
THE PERMIAN PERIOD
PHYSICAL EVENTS OF THE PERMIAN IN NORTH AMERICA . 269
THE PERMIAN IN OTHER CONTINENTS . . . . 270
THE PERMIAN SYSTEM IN CANADA. . . . .271
LIFE OF THE PERMIAN . *. . .... . 272
CHAPTER XI
SUMMARY OF THE PALEOZOIC ERA
CONTENTS xiii
CHAPTER XII
THE MESOZOIC ERA— THE TRIASSIC PERIOD
PAGE
GENERAL FEATURES OF THE MESOZOIC . . ... . 278
THE TRIASSIC PERIOD . . . '. .' . '• . . 279
PHYSICAL EVENTS OF THE TRIASSIC IN NORTH AMERICA ~\'. 279
THE TRIASSIC SYSTEM IN CANADA ""Y . '. *. '' ". r 280
LIFE OF THE TRIASSIC . . . V •;-•--,- - ••;••-• ,L. 283
CHAPTER XIII
THE JURASSIC PERIOD
PHYSICAL EVENTS OF THE JURASSIC IN NORTH AMERICA . 288
THE JURASSIC SYSTEM IN CANADA . . . . .289
The Jurassic igneous rocks of British Columbia . . . 290
LIFE OF THE JURASSIC ........ 292
Jurassic plants . . . . . . . 293
Jurassic invertebrates . ... . . . . 294
Jurassic vertebrates . . . . , . . . 299
CHAPTER XIV
THE CRETACEOUS PERIOD
THE EUROPEAN CRETACEOUS ...... 305
PHYSICAL EVENTS OF THE CRETACEOUS IN NORTH AMERICA . 306
THE CRETACEOUS SYSTEM IN CANADA . . . . . 309
LIFE OF THE CRETACEOUS . . . . . . .314
Cretaceous plants . . . . . . ..314
Cretaceous invertebrates . . . . . . • . . 314
Cretaceous vertebrates, dinosaurs, etc. . -. . .318
CHAPTER XV
SUMMARY OF THE MESOZOIC ERA
xlv ELEMENTARY GEOLOGY
CHAPTER XVI
THE CENOZOIC ERA— THE TERTIARY PERIOD
PAGE
THE CENOZOIC ERA . . . ,r. ^ ... 330
THE TERTIARY PERIOD . . . . .. . 330
CLASSIFICATION OF THE TERTIARY PERIOD *., . . . _. . 331
PHYSICAL EVENTS OF THE TERTIARY IN NORTH AMERICA . 332
THE TERTIARY SYSTEM IN CANADA . - . . • • 334
LIFE OF THE TERTIARY . . . . . . i . 337
Tertiary mammals . . . .. . -338
Extinct groups of Tertiary mammals . . . . . 342
The development of typical races of modern mammals . 343
CHAPTER XVII
THE QUATERNARY PERIOD— THE PLEISTOCENE EPOCH
OLDER CLASSIFICATION OF THE PLEISTOCENE . :. : . . 347
THE GLACIAL PERIOD . :", . ''" . . * . i -.^ :,').'.% ^
Extent of glaciation in North America •*.' . . r •>"•'. • '':V 348
Conditions during the glacial period . -. . ' . ' ' v ', 351
Interglacial periods . . . . . , r vi.:^ 353
The withdrawal of the ice sheets and the formation of glacial
lakes .... . .354
THE MARINE EPISODE OR CHAMPLAIN PERIOD . ' •» . . 356
PHYSIOGRAPHIC EFFECT OF THE GLACIAL PERIOD . - . . 357
THE PLEISTOCENE IN OTHER REGIONS . . . 358
THE LIFE OF THE PLEISTOCENE . • . . , . . . 359
Man's appearance in geology . . ,~ . . 360
LIST OF ILLUSTRATIONS
FIG. PAGE
1. GROUND FIGURES OF THE Six SYSTEMS OF CRYSTALS . 8
2. CRYSTAL OF QUARTZ ....... 9
3. CRYSTAL OF ORTHOCLASE FELDSPAR . . . .10
4. CRYSTAL OF PYROXENE . . . . . .11
5. CRYSTAL OF HORNBLENDE . . . . . .11
6. GRANITE, ILLUSTRATING THE "GRANITIC" OR EVEN-
GRAINED STRUCTURE OF DEEP-SEATED IGNEOUS ROCKS 23
7. JASPER CONGLOMERATE ...... 30
8. TYPICAL GNEISS, KILLALOE, HAGERTY TOWNSHIP, ONT. . 34
9. THE THREE STANDING COLUMNS OF THE TEMPLE OF
JUPITER SERAPIS, NEAR NAPLES .... 40
10. RAISED BEACHES, SPITZBERGEN . . . . 41
11. SEISMOGRAM OF SAN FRANCISCO EARTHQUAKE, APRIL 18, 1906 47
12. CRATER OF MOUNT KILAUEA, HAWAII .... 52
13. MONT PELEE ", . . . . . . -54
14. ERUPTION OF NGAURUHOE, NEW ZEALAND, IN 1914 . . 56
15. CRATERS AND CINDER CONES, MOUNT ETNA ... 57
16. HONEYCOMB WEATHERING IN STRATIFIED ROCKS, LAKE
TIMISKAMING, QUEBEC ...... 67
17. TALUS FORMED BY ACTION OF FROST, NlPIGON RlVER, ONT. 68
1 8. EARTH PILLARS DUE TO RAIN EROSION OF BOULDER CLAY,
ROCKY MOUNTAINS . ... . . .69
19. UNDERGROUND WATERS . ^. . . . 70
20. LANDSLIP, FRANK, ALBERTA . » . . . .71
21. CAVE, NEW ZEALAND . . . .... 73
22. CANYON OF ABITIBI RIVER, ONTARIO .... 77
23. MEANDERS IN FLOOD PLAIN, DON RIVER, TORONTO, ONTARIO 78
24. DELTA OF THE MACKENZIE RIVER, ARCTIC OCEAN, AND OF
THE KAMINISTIQUIA RIVER, THUNDER BAY, LAKE
SUPERIOR . . . . . . . .80
25. EMPEROR FALLS, MOUNT ROBSON, B.C. 81
26. MOUNTAIN TORRENT, NAKVAK, LABRADOR ... 83
27. WAVES, NEWCASTLE, NEW SOUTH WALES . . .85
28. WAVE EROSION, CAPE BLOMIDON, NOVA SCOTIA . . 86
29. A HOOK. THE "ISLAND" AT TORONTO, ONTARIO . . 87
30. A MAP OF THE WORLD, SHOWING THE PRINCIPAL OCEAN
CURRENTS ........ 89
31. TIDE AT WOLFVILLE ON BAY OF FUNDY . . -91
32. BORAX LAKE AND THE VOLCANO OLLEGUE, BOLIVIA .' 94
XV
xvi ELEMENTARY GEOLOGY
FIG. PAGE
33. ICE RAMPART, LAKE SIMCOE, ONTARIO . .. . - . 96
34. GLACIER ON MOUNT BALFOUR, ROCKY MOUNTAINS, SHOWING
NEVE FIELDS, ICE FALLS, AND MEDIAL MORAINES . 97
35. ICE CAVE AND RIVER AT END OF YOHO GLACIER, B.C. . 98
36. MEDIAL MORAINE, ALASKAN BOUNDARY . . . . 99
37. TERMINAL MORAINE, MAIN GLACIER, MOUNT ROBSON, B.C. 99
38. BOULDER CLAY WITH STRIATED STONES, TORONTO, ONT. . 100
39. STRIATED STONE FROM BOULDER CLAY AT TORONTO, ONT. . 100
40. ROCHE MOUTONNEE AND STRIATED SURFACE, COPPER CLIFF,
ONTARIO . . ... . *.. • . . .. 101
41. CIRQUE NEAR MOUNT TETRAGONA, LABRADOR . . 102
42. SAND DUNE NEAR WELLINGTON, ONTARIO . . . 104.
43. BAD LANDS SHOWING WIND SCOUR, RED DEER RIVER,
ALBERTA ' . . ' -.-.:.' . . .• . . 105
44. TERTIARY LIMESTONE WITH SHELLS . , . . in
45. STRATIFICATION OF LORRAINE SHALE AND LIMESTONE,
HUMBER RIVER, TORONTO ' . . . .- • . . 115
46. CROSS BEDDING IN SANDSTONE, DUE TO WAVES AND CUR-
RENTS, THOUSAND ISLANDS, ONTARIO .. ; . 116
47. TIDE RIPPLES, SOURIS, PRINCE EDWARD ISLAND . .116
48. JOINTS IN LIMESTONE, NAPANEE, ONTARIO ... . .117
49. CONCRETIONS OF CARBONATE OF LIME FROM PLEISTOCENE
CLAY, TORONTO, ONTARIO '. . . . . * . 1 1 8
50. DIAGRAM SHOWING STRIKE AND PIP . . . .119
51. OPEN SYMMETRICAL FOLD SHOWING AN ANTICLINE OR UP-
WARD BEND AND A SYNCLINE OR DOWNWARD BEND. 120
52. PART OF FOLDING MOUNTAIN, ATHABASCA GAP, ROCKY
MOUNTAINS, SHOWING A COMPLEX SYNCLINE . . 120
53. OVERTURNED FOLD, CLEARWATER RIVER . . . 121
54. A MONOCLINE . 121
55. FOLDING UNDER THRUST FAULT, CLEARWATER RIVER . 122
56. NORMAL FAULTS, SHOWING A HORST AND A GRABEN . 122
57. NORMAL FAULT NEAR NIPIGON, ONTARIO . . . 123
58. THRUST FAULT NEAR GHOST RIVER, Bow PASS . .124
59. MODERN FAULT CONNECTED WITH AN ALASKAN EARTHQUAKE 124
60. DISCORDANCES . , . . . . . . 125
61. DlSCONFORMITY .... . ... . . . . 125
62. UNCONFORMITY, UTAH . . . ... . 126
63. PA-HOE-HOE LAVA, KILAUEA, HAWAII . . •- • 126
64. AA LAVA, ETNA . . . . . . .- . 127
65. PILLOW AND AMYGDALOIDAL STRUCTURE, SUDBURY, ONT. . 128
66. DIABASE DIKES, SAGLEK, LABRADOR . . . . 129
67. IDEAL CROSS SECTION OF A LACCOLITH WITH SHEETS AND
DIKES . . . . . , . . . 130
68. THE SUDBURY BASIN, ONTARIO . . . ^ . I31
LIST OF ILLUSTRATIONS xvii
FIG. PAGE
69. PLAN AND CROSS SECTION OF A BATHOLITH . . -132
70. BASALTIC COLUMNS NEAR MOUNT GARIBALDI, B.C. . 133
71. SHEETING AND JOINTING IN GRANITE, Fox ISLAND, B.C. 134
72. OUTLINE MAP OF CANADA SHOWING IN BLACK THE CHIEF
AREAS OF PRE-CAMBRIAN ROCKS . . . .163
73. TIMISKAMING SERIES, PORCUPINE, ONTARIO . . . 173
74. STRIATED STONE FROM COBALT TILLITE . . . .176
75. TILLITE (BOULDER CONGLOMERATE) OF COBALT SERIES
RESTING ON KEEWATIN GREENSTONE, COBALT, ONT. 177
76. PAL^OGEOGRAPHIC MAP OF NORTH AMERICA IN LOWER
CAMBRIAN TIME ....... 186
77. SKETCH MAP OF EASTERN CANADA SHOWING THE CHIEF
AREAS OF CAMBRIAN ROCKS . . . . .188
7§. LAKE LOUISE, ROCKY MOUNTAINS . . . .190
79. A TRILOBITE DISSECTED TO SHOW CHIEF POINTS OF THE
ANATOMY . . . . . . . 192
80. DIAGRAMS OF THE HEADS OF THE THREE TYPES OF
TRILOBITES .. . . . . ... 192
81. OLENELLUS, THE TYPICAL TRILOBITE OF THE LOWER
CAMBRIAN . . , . . . ... . 193
82. STRUCTURE OF THE RECENT BRACHIOPOD, MEGALLANIA
FLAVESCENS . . . . . . . . 194
83. FOUR TYPES OF BRACHIOPODS . . . . . 195
84. CAMBRIAN FOSSILS OF BRITISH COLUMBIA . . . 197
85. PAL^EOGEOGRAPHIC MAP OF NORTH AMERICA IN UPPER
ORDOVICIAN TIME ....... 200
86. SKETCH MAP OF EASTERN CANADA SHOWING IN BLACK THE
CHIEF AREAS OF ORDOVICIAN ROCKS . . . 203
87. ORDOVICIAN CORALS . ... . . . 205
88. ORBOVICIAN GRAPTOLITES . ,>=.•'• . . . . 206
89. ORDOVICIAN CRINOIDS AND CYSTIDS ». , . . . 207
90. ORDOVICIAN BRACHIOPODS . . . . . . 209
91. STRUCTURE OF LONG-CELLED OR TUBULAR BRYOZOANS . 210
92. ORDOVICIAN OSTRACODS AND BRYOZOANS . -. . 211
93. ORDOVICIAN GASTROPODS . . . . . . 212
94. ORDOVICIAN PELECYPODS . . . . . .213
95. ORDOVICIAN PELECYPOD . . . . . .213
96. NAUTILUS POMPILIUS, A RECENT NAUTILOID, WITH THE
SHELL REMOVED ON ONE SIDE. . . . .214
97. ORDOVICIAN NAUTILOIDS . . . . . .214
98. ACTINOCERAS CREBRISEPTUM FROM THE LORRAINE ROCKS
AT TORONTO ........ 215
99. ORDOVICIAN TRILOBITES . . . . .215
TOO. ORDOVICIAN TRILOBITES . . . . . .216
101. THE NIAGARA CUESTA . . . . . . .219
xviii ELEMENTARY GEOLOGY
FIG. PAGE
102. SKETCH MAP OF EASTERN CANADA SHOWING IN BLACK THE
CHIEF AREAS OF SILURIAN ROCKS . "•••;* '• . . 220
103. SKETCH MAP OF CENTRAL CANADA SHOWING THE AREAS
COVERED BY PALAEOZOIC ROCKS . " V ' '*'* ' . ':">.."• 221
104. SILURIAN CORALS . . * . .. : '. ; ;•'<*. . 223
105. SILURIAN DENDROID GRAPTOLITE * -. , • . '. '•••>. ' „'.' 224
106. STROMATOPOROIDS OF THE SILURIAN.' •.*• .-• . . 225
107. SILURIAN CRINOIDS AND CYSTIDS . . . ' ', '. . 225
108. SILURIAN BRACHIOPODS . . , .,.'.. 226
109. SILURIAN GASTROPODS . ." •. . . . " . -227
no. SILURIAN PELECYPODS AND CEPHALOPODS . , . 228
in. SILURIAN TRILOBITES . * " . ' . " . .... 229
112. EURYPTERUS REMIPES . . .;'.;.' ; • ' -V-*'* . 230
113. PAL^EOGEOGRAPHIC MAP OF NORTH AMERICA IN MIDDLE ,
AND UPPER DEVONIAN TIME . . . . s 4- 231
114. SKETCH MAP OF EASTERN CANADA SHOWING THE CHIEF
AREAS OF DEVONIAN ROCKS . .'./-.- . 234
115. SILURIAN AND DEVONIAN PLANT •. •...,. . 239
116. SLAB OF ONONDAGA LIMESTONE FROM ONTARIO SHOWING
THE PROFUSION OF FOSSILS •. •. ". : . -: . 240
117. DEVONIAN CORALS . . •= ' N. . . i 241
118. DEVONIAN CRINOIDS AND BLASTOIDS •. . . J . 242
119. DEVONIAN BRACHIOPODS ' . . . ^ . - . 243
120. DEVONIAN PELECYPODS AND GASTROPODS . ' , . 243
121. DEVONIAN CEPHALOPODS .' ' ?.. . .. • . . 244
122. DEVONIAN TRILOBITES . •. .. . ' - -. -. . 244
123. TYPICAL DEVONIAN OSTRACODERM . •'«• ' /. . , . 245
124. JAWS OF THE "TERRIBLE FISH" ; .; ' ." . . 246
125. DEVONIAN FISH . • . . •.. ' . .-. . . 247
126. DEVONIAN OSTRACODERM • . ' . . . „ . 248
127. KETTLE POINT, LAKE HURON . •• . .« . . 248
128. SKETCH MAP OF EASTERN CANADA SHOWING THE EXTENT OF
CARBONIFEROUS ROCKS .. ..o^A . ; . . 255
129. ROCKY MOUNTAINS NEAR BANFF, ALBERTA .^ . . . 256
130. CARBONIFEROUS FERNS AND CYCAS-FERNS . . . 258
131. CARBONIFEROUS TREE-FERNS . f . . . . . 259
132. CARBONIFEROUS TREES . -.. •. .; . . 260
133. THE TYPICAL CARBONIFEROUS CORAL, LITHOSTROTION
CANADENSE • . • '.. . • '. ' . ,. . . . 262
134. CARBONIFEROUS MARINE INVERTEBRATES . .'-. . . 263
135. CARBONIFEROUS ARTHROPODS. . . . . . 264
136. WING OF HAPLOPHLEBIUM BARNESII • ." . . r . 265
137. CARBONIFEROUS FISH . . . V •* ;. . 266
138. CARBONIFEROUS AMPHIBIA . . . i V . 267
139. THE GLOSSOPTERIS FLORA . • . ••=-«-..-' - . ' - . - . 273
LIST OF ILLUSTRATIONS xix
FIG. PAGE
140. PERMIAN AMPHIBIAN ..... . 273
141. PERMIAN REPTILE ....... 274
142. TRIASSIC TRAPS OF NOVA SCOTIA, CAPE BLOMIDON . .281
143. TRIASSIC INVERTEBRATES . . . . . . 284
144. TRTASSIC CRUSTACEAN ....... 285
145. TRIASSIC WATER REPTILE . . . . . 286
146. PRIMITIVE TRIASSIC CROCODILE ..... 286
147. TRIASSIC VERTEBRATES ....... 287
148. SKETCH MAP OF BRITISH COLUMBIA .... 291
149. MESOZOIC PLANTS ........ 293
150. MODERN CYCADS ........ 294
151. LIASSIC CRINOID ........ 295
152. JURASSIC PELECYPODS ....... 296
153. SLAB FROM THE JURASSIC OF ENGLAND .... 296
154. LIASSIC AND JURASSIC AMMONITES ..... 297
155. LIASSIC AND JURASSIC BELEMNITES . . . . 298
J56. JURASSIC DECAPOD ....... 299
157. SHINING-SCALED GANOIDS OF THE JURASSIC . . . 299
158. MESOZOIC FLYING REPTILES ...... 302
159. ARCH^OPTERYX MACRURA, THE FIRST BIRD (JURASSIC) . 303
160. SKETCH MAP OF NORTH AMERICA IN CRETACEOUS TIME . 308
161. SKETCH MAP SHOWING THE CRETACEOUS AND TERTIARY
ROCKS OF THE GREAT PLAINS . . . . .311
162. CRETACEOUS CRINOID . . . . . . .315
163. CRETACEOUS PELECYPODS . . . . . . 316
164. CRETACEOUS PELECYPOD . . . . . -317
165. CRETACEOUS GASTROPODS . . . . . .317
166. CRETACEOUS ECHINIDS AND CEPHALOPODS . . .319
167. UPPER CRETACEOUS PLESIOSAUR . . . . 320
168. CRETACEOUS MOSASAUR . . . . . . • . 320
169. THE GREAT AMPHIBIOUS DINOSAUR, BRONTOSAURUS
EXCELSUS . . . . . . . .321
170. THE GREAT AMPHIBIOUS DINOSAUR, DIPLODOCUS CARNEGII 321
171. CRETACEOUS CARNIVOROUS DINOSAUR, GORGOSAURUS
LIBRATUS ........ 322
172. CRETACEOUS CARNIVOROUS DINOSAUR, TYRANNOSAURUS
REX (HEAD) ........ 322
173. CRETACEOUS TRACHODONT DINOSAURS .... 323
174. EUROPEAN CRETACEOUS BEAKED DINOSAUR . . 324
175. CRETACEOUS HORNED DINOSAURS ..... 324
176. CRETACEOUS HORNED DINOSAURS ..... 325
177. CRETACEOUS ARMOURED DINOSAUR. .... 326
178. CRETACEOUS TURTLE ....... 328
179. CRETACEOUS WADING BIRD ...... 329
1 80. MAP SHOWING THE NATURAL SUBDIVISIONS OF SOUTHERN
BRITISH COLUMBIA ....... 336
xx ELEMENTARY GEOLOGY
FIG. PAGE
181. CANADIAN TERTIARY FISH . . . . .' . 338
182. PRIMITIVE BASAL EOCENE MAMMAL . . . . 340
183. AN UPPER EOCENE PAL^OTHERE . >.;. . . . 342
184. THE EVOLUTION OF THE HORSE . . . . . 343
185. THE EVOLUTION OF THE HORSE « . . . . 344
1 86. THE EVOLUTION OF THE ELEPHANT FAMILY DURING THE
TERTIARY . . . . ' . . . . 345
187. MIOCENE APE . . . ... . . . . 346
1 88. GLACIAL MAP OF NORTH AMERICA . .. . . . 349
189. INTERGLACIAL BEDS . . . v ... .351
190. Two BEDS OF TILL WITH STRATIFIED SAND BETWEEN . 352
191. AN EXTINCT MAPLE . . . . . . • . . 353
192. EXTINCT BEETLES. . . . . „ . . . 354
193. SKETCH MAP OF POST-GLACIAL LAKES .... 355
194. A MASTODON * . . . . . . . 358
195. THE GREAT GROUND SLOTH OF THE PLEISTOCENE . . 359
196. PLEISTOCENE CARNIVORE . ... . . 360
197. PLEISTOCENE MARSUPIAL . . . ... .361
ELEMENTARY GEOLOGY
PART I
PHYSICAL GEOLOGY
CHAPTER I
INTRODUCTORY
THE earth is man's home, his workshop, his storehouse, his
playground, the environment which shapes him to what he
is; and every intelligent man should know something of it,
particularly in regard to his immediate surroundings and his
own country.
The earth is only a modest planet in a solar system of
quite moderate dimensions, as solar systems. go in the uni-
verse; but it is the only planet we can ever know at all
intimately, and small as it is, it is full of interest, and has a
thrilling history that accounts for all about us and even for
the race of man himself. No one is really educated in the
modern sense who does not know something of the solid
ground beneath his feet and of the shaping of the hills and
valleys and plains among which he lives. His house, his tools
and instruments, and even his tableware are usually made of
materials drawn from the earth and therefore taken from the
realm of geology. He cannot walk the streets of a city with-
out seeing everywhere things that have a geological origin ; and
when he tills the soil or makes the bricks of everyday life
he is handling geological materials and doing geological
work, whether he knows it or not.
Whether from the economic or the intellectual side, in
war or in peace, man is perpetually confronting geological
factors that are of vital importance to him, and of which
he cannot be ignorant without loss of efficiency and loss
of a mental stimulus.
&<:^.t -E.LEMENTARY GEOLOGY
Geology is the science of the earth, and the earth is many
sided, so that it has, perhaps, the widest affiliations of any of
the sciences and is itself almost a bundle of sciences, there are so
many avenues along which its researches may be directed. On
this account geologists by profession are bound to specialise,
since no one man can be equally proficient in all departments
of so protean a subject.
SUBDIVISIONS OF GEOLOGY
Geology deals with the materials of which the earth is made,
the forces that operate upon them, the structures which result
from this operation, the distribution of the rocks forming
the earth's crust, and the history of the earth itself and of
the plants and animals which have inhabited it during the
different ages.
The usual divisions of geology as treated in a text-book are
as follows:
Lithology. The study of rocks and of the minerals of which
they are composed.
Dynamic Geology. A consideration of the forces which
have shaped and still are shaping the earth.
Structural Geology. Dealing with the architecture of the
earth's crust.
Historical and Stratigraphical Geology. Showing the order
and distribution of the different series of rocks, and
unravelling the history of the earth and its inhabitants
as disclosed in the rocks.
Lithology draws on the cognate science of mineralogy for
aid; Dynamic Geology makes use mainly of the principles of
physics and chemistry, but touches also zoology and botany;
Structural Geology deals with the attitude and arrangement
of rocks; and Historical Geology derives much aid from
palaeontology, the science which deals with fossils. Historical
Geology may be said to begin with astronomy and to end
with physiography, or physical geography, which deals with
the present surface features of the earth.
INTRODUCTORY
THE EARTH AS A WHOLE
The earth is one of the minor planets of the solar system,
with a diameter of almost 8000 miles. It is often called a
globe or sphere, but not quite correctly, since it is flattened
at the poles. It approaches the form of a rotating mass of
fluid, which would be called an "oblate spheroid" or an
"ellipsoid of rotation," but does not quite attain perfection,
since its surface has irregularities, elevations, and depressions,
with extremes amounting to eleven miles, and its equatorial
circumference is not exactly a circle. The polar diameter is
given as 7925-6 miles and the average equatorial diameter
as 7899-1, the polar flattening representing half the difference,
or a little over thirteen miles.
THE EARTH'S MOTIONS
The planetary motions of the earth, its annual revolution
about the sun and its diurnal rotation about its axis, are of
great importance as influencing tides, currents, winds, and
climates; and the fact that the earth's axis is inclined 23*5
degrees to the plane of its orbit is also a matter of interest.
A change in any of these relations would have serious effects.
There is reason to believe that tidal friction is very gradually
slowing down the energy of rotation, and it has been suggested
that in early times the earth rotated in six hours instead of
twenty-four. Such a difference would greatly alter the shape
of the earth, increasing the equatorial bulge and shortening
the polar diameter. There is no doubt that any variation in
the shape of the earth due to the lengthening of the day, as
suggested, would result in bucklings of the crust such as
would make mountain ranges and depressions in the sea
bottom. A more rapid rotation would speed up a number of
terrestrial activities such as tides and winds, and make them
more effective geological agencies.
A change in the inclination of the earth's axis would pro-
foundly affect geology. If the axis stood at right angles to
the plane of the earth's orbit, there would be no alternation
of seasons, with all which that implies ; and other conceivable
4 ELEMENTARY GEOLOGY
arrangements might have tremendous effects. Some geologists
have suggested a change in position of the poles to account
for the occurrence of ice ages, times when great ice sheets
covered parts of the temperate zones and even advanced into
the tropics, but there is a serious difficulty in the way of such
a change. The rotating earth is a gyroscope on a huge scale
and would violently resist any shifting in the direction of its
axis of rotation, so that a sudden variation of the sort would
probably tear the earth to pieces.
The geological record does not indicate any remarkable or
rapid change in the earth's motions, and, in fact, shows a
surprising uniformity in its relations to the other members of
the solar system. There is no evidence, for instance, of greater
tidal activity in the earliest water-formed rocks; and there is
no proof that the sun radiated more heat to the earth a
hundred million years ago than it does now; for liquid water
and great sheets of ice were at work then as now.
THE COMPOSITION OF THE EARTH
So far as we know the earth's composition by direct study
it is formed of various rocks, which will be described later,
such as granite or limestone or sandstone. The average
specific gravity of these rocks is 2-6 or 2-7, and the heaviest
rocks known to occur on a large scale do not much exceed
3 in specific gravity; yet the earth as a whole has a
specific gravity of 5-5 or 5-6— nearly double as much. Evi-
dently the materials below the surface are much heavier than
those within our reach : this has been explained by supposing
that the central parts consist of heavier elements, such as
iron and nickel, which occur only in relatively small amounts
in the earth's crust, the only part which we can examine.
It has been suggested, however, that the same materials as
make up the crust might be greatly compressed by the weight
of the overlying rocks, and so attain a higher specific gravity.
Perhaps a combination of the two theories is best.
Since the earth, as known to us, consists of rock, it may be
called the " lithosphere," from the Greek word for rock ; but we
can actually examine only a little more than one-fourth of its
INTRODUCTORY 5
surface, the rest being beneath the sea. The incomplete
spherical covering of water may be called the "hydrosphere."
Above all rises a sea of air, reaching indefinitely upwards,
which is, of course, the "atmosphere." Geology is largely
occupied in studying the interactions of the atmosphere and
hydrosphere upon the lithosphere. Beneath the lithosphere
some geologists place an " asthenosphere " (strengthless)
capable of flow like a plastic body, while the unknown interior
may be called the "centrosphere."
Of the many known chemical elements comparatively few
play any important part in building the earth's crust, and
there seems to have been a strange partiality shown for eight
of theiru — oxygen, silicon, aluminium, iron, calcium, mag-
nesium, sodium, and potassium — which make up ninety-eight
per cent, of the rocks examined, oxygen alone forming fifty
per cent. Carbon, one of the most important substances in
practical life, forms less than one-fifth of one per cent, of the
rocks available to man; and copper, lead, zinc, and the other
economic metals, leaving out iron, provide only minute frac-
tions of one per cent. It may be that the balance is restored
in the earth's interior, the heavier elements gravitating towards
the centre.
Of the chemical compounds, silica, a compound of silicon
and oxygen, outweighs the others put together and enters
largely into the composition of many rocks.
CHAPTER II
MINERALS AND ROCKS '
THE geological history of the earth is recorded in the rocks.
It is obvious that the nature of the rocks, and the chemical
and physical changes which they have undergone, will con-
tribute in no small degree to the main object in view— the
working out of the history of the earth.
MINERALS
All matter is made up of certain primary substances known
as elements, of which only a few occur as such in the make-up
of the earth. Gold, silver, copper, and arsenic are among the
elements that are found in the rocks; when so found they
are called native gold, silver, copper, etc. On the other hand,
iron, which is a very common element, occurs with extreme
rarity as native iron. Most of the elements never occur native
but united with one another to form chemical compounds.
These compounds are made up of very definite amounts of
the elements composing them, and they differ entirely from
any of the constituent elements. For instance, water is made
up of two colourless gases, oxygen and hydrogen, united in
the proportion of eight to one; and most of the iron of com-
merce is made from a red or black brittle substance composed
of iron and a definite proportion of this same colourless gas,
oxygen. Commercial iron is made by subjecting this substance
to furnace operations whereby it is forced to let go the oxygen
which it contains. If a piece of iron is allowed to lie out in
the weather it slowly rusts and eventually crumbles away to
a reddish powder. Nature has claimed her own again, and
the man-made iron has gone back again into the union with
oxygen which is natural to it. Processes of this kind have
been going on in nature's workshop throughout the geological
ages, with the net result that the earth, as far as we know it,
1 A proper conception of minerals and rocks can be acquired only by
seeing and handling specimens. The few minerals and rocks herein
described are treated in the merest outline only. The student is advised
to consult any of the standard works on mineralogy and petrography.
MINERALS AJsfD ROCKS 7
is made up of a small amount of native elements and a great
amount of chemical compounds. Both of these are minerals,
and that branch of geological science which deals with them
is mineralogy.
It is evident that the chemical composition of a mineral is
a matter of the first importance, and without at least an
elementary knowledge of chemistry it is difficult to properly
understand minerals. Fortunately, however, minerals are
possessed of very characteristic physical properties, whereby
they may be easily recognised even by one to whom their
chemical nature is entirely unknown. A student need not
despair of acquiring a fair knowledge of minerals even if his ac-
quaintance with chemistry is limited. In the brief descriptions
of minerals given herein only a knowledge of the names of the
elements, and of such common substances as silica, alumina,
lime, and magnesia is presupposed on the part of the reader.
The chief physical properties made use of for the description
and identification of minerals are as follows:
LUSTRE. Some minerals have the appearance of metal and
are said to have a metallic lustre; others, such as a piece of
common limestone, have no resemblance to a metal and are
said to have a non-metallic lustre. These are the two chief
lustres; others of less importance are pearly, vitreous, resinous,
silky, and earthy — terms which sufficiently explain themselves.
COLOUR. The actual colour of a mineral is important,
particularly when combined with metallic lustre.
STREAK. The streak is the colour of the finely powdered
mineral and is often different from that of the mineral itself.
This property is very constant and is of more value than
colour in the case of minerals with non-metallic lustre. The
streak may be obtained by crushing a small piece of the mineral
or by drawing a fine file across it.
HARDNESS. This property is of great value. In order to
express it in short form a scale has been established using the
numerals i to 10 to indicate increasing degrees of hardness.
A mineral with the hardness i can be scratched by the thumb
nail; 3 is about equal to copper; 5 scratches glass feebly;
6 scratches glass easily; 7 is quartz or rock crystal which is
much harder than glass; 8, 9, and 10 are harder than quartz.
WEIGHT. The weight, or more properly the specific gravity,
8
ELEMENTARY GEOLOGY
of a mineral is fairly constant. Common rock-making minerals
vary from 2-5 to 3 or a little more. The ores of the metals are
heavier; they average about 6 or 7, but in some cases run
considerably higher — for instance, native gold has a specific
gravity of 19-5.
CRYSTAL FORM. Nearly all minerals assume a definite shape
FIG. I. GROUND FIGURES OF THE SIX SYSTEMS OF CRYSTALS
By modifications of these forms, the replacement of angles and edges by other planes, all
known crystals may be derived.
which is extremely characteristic and which in most cases
would suffice for their determination in the hands of an
expert. Unfortunately, when minerals occur in masses the
crystals are so closely pressed together that their form is
obscured, but never altered. Crystals are bounded by flat
planes which meet each other in angles of absolute constancy.
Several systems of crystals are recognised depending on the
degree of symmetry they present. In some the planes are
arranged regularly about a centre (cubic or regular system);
MINERALS AND ROCKS
in others in a tetrameral manner about a long axis (tetragonal
system) ; in others in a hexagonal manner about a long axis
(hexagonal system) ; in others about three axes of different
lengths set at right angles to one another (rhombic system) ;
in others about three unequal axes of which only two are
at right angles (monoclinic system) ; and finally about three
unequal axes none of which is at right angles to another
(triclinic system).
CLEAVAGE. Many crystals have a tendency to split parallel
to certain planes. Even when the form cannot be made out
this property is useful in determining minerals as it is very
constant.
From 1200 to 1500 minerals in all are known to science; of
these a comparatively small number compose the great bulk
of the earth's crust. The commonest minerals are those which
are aggregated together to make up rocks, and are known as
rock-forming minerals. In smaller amount occur the minerals
which are used as ores of the metals. Other minerals worthy
of mention in a work of this kind are those which are used
for the production of useful substances of a non-metallic
nature. The remaining minerals are of little importance from
the present point of view. The more common minerals will
be briefly considered in groups as below:
I. COMMON MINERALS FORMING IGNEOUS ROCKS
QUARTZ. This is the commonest of all minerals and makes
up a large part of the rocks of the earth:
it is composed of silica, a compound of the
elements silicon and oxygen.
Quartz forms six-sided prisms with a six-
sided pyramid on each end; therefore, it is
said to crystallise in the hexagonal system.
There is no cleavage as the mineral breaks
irregularly. The lustre is non-metallic and
vitreous; normally colourless and trans-
parent, quartz is frequently tinged by the
presence of foreign matter. The streak is
colourless; the hardness 7; and the specific
gravity about 2-65.
Quartz is a constituent of granite and of many other
FIG. 2. CRYSTAL
OF QUARTZ
10
ELEMENTARY GEOLOGY
igneous rocks; it also makes up a large part of most sand-
stones. The gangue or vein-filling material of the gold mines
of northern Ontario is quartz, and the coloured variety known
as amethyst is obtained along the Fundy shore of Nova Scotia
and the north shore of Lake Superior.
FELDSPARS. This group of minerals comprises several
related chemical compounds of silica and alumina with potash,
soda, and lime. A number of minerals are
included, but they may be divided into two
classes: (i) orthoclase or potash feldspar,
and (2) plagioclase or soda-lime feldspar.
The physical properties are much alike in
all the feldspars: the lustre is non-metallic;
the colour variable, but usually light —
white, pink, bluish, etc. ; the streak colour-
less; the hardness 6; and the specific
gravity 2-4 to 27.
The two kinds of feldspar differ slightly in
their crystal form ; orthoclase is monoclinic
FIG. 3. CRYSTAL and plagioclase triclinic. Both varieties
OF ORTHOCLASE have distinct cleavage, a property which is
of great use in distinguishing them from
quartz which has no cleavage. The character of the cleavage
is also of great use in distinguishing between the two kinds
of feldspar, as in the case of orthoclase it is smooth, whereas
the cleavage faces of plagioclase show fine parallel striations.
Feldspar of one kind or the other is a constituent of nearly
all the igneous rocks, the classification of which depends very
largely on the kind of feldspar present. One must remember
that the distinction between the two kinds of feldspar is of
prime importance and not merely a matter of detail.
Feldspar is used in the ceramic arts to a large extent, also
in metallurgical operations, and for many specific purposes.
Orthoclase is a possible source of potash, but its separation is
a matter of difficulty not yet achieved on a commercial scale.
Large feldspar mines are worked to the north of Kingston
in Ontario.
NEPHELINE. This mineral is related in composition to the
feldspars, but it crystallises in the hexagonal system. Nephe-
Une is a constituent of igneous rocks of much rarer occurrence
MINERALS AND ROCKS
ii
than feldspar; its mention here is justified by its presence in
important masses of rock in Ontario.
PYROXENE. This mineral is a complicated compound of
silica with lime, magnesia, iron, manganese, and other sub-
stances; alumina also is present in many
varieties. The crystals are of the mono-
clinic type and have a pronounced cleavage
parallel to two planes which meet at an
angle of 87° 5'; this property is of great
value as a means of determination, as
broken pieces of pyroxene will be sure to
present fragments on which this angle
may be observed.
The lustre is non-metallic and rather
vitreous; the colour varies from light \/^
green to black; streak colourless or light FIG. 4. CRYSTAL OF
greyish green; hardness 5 to 6; specific PYROXENE
gravity 3-23 to 3-5, indicating a heavier mineral than quartz
or feldspar.
Pyroxene is a very common rock-forming mineral and is
particularly abundant in the dark-coloured, heavy igneous
rocks. Many varieties are known, such as augitc and diallage.
Hypersthene is a mineral related to pyroxene in composition,
but crystallising in the rhombic system; it is sometimes
called rhombic pyroxene. The common py-
roxene, augite, is most likely to be mis-
taken for hornblende, but it may easily be
distinguished by the angle of cleavage.
HORNBLENDE. The chemical composition
of this mineral is very similar to that of
pyroxene; its crystal form also is similar,
but differs in the important respect that the
cleavage angle is 124° 30' instead of 87° 5'
as in pyroxene. This difference of angle
may usua»y be relied on to distinguish
between the two minerals. The other physi-
cal properties are practically the same as those of pyroxene.
Hornblende is a common constituent of the igneous rocks,
but it is less common than pyroxene in the very dark rocks;
on the other hand, it is more frequent in the intermediate
and light-coloured rocks,
12 ELEMENTARY GEOLOGY
MICA GROUP. This group contains a number of complicated
compounds of silica, alumina, lime, magnesia, potash, and
other substances in less amount. While the crystal forms
belong to different systems in the different micas they all
approximate to six-sided prisms and they all have a very
strong tendency to cleave across the prism, whereby the
familiar sheets of mica are broken off.
The lustre is sometimes sub-metallic, pearly, or even
vitreous; the colour varies with the varieties, from clear
transparent to almost black; the streak is colourless or very
lightly tinted; the hardness seldom exceeds 3; the specific
gravity is usually between 2-7 and 3-1.
Many varieties based on different chemical composition and
slightly different physical properties are known: the chief of
these are Uotite or black mica with much iron and magnesia,
Muscovite or white mica with much potash, and phlogopite or
amber mica with magnesia and potash.
Mica is a very common constituent of rocks; when black,
it may be mistaken in a rock for pyroxene or hornblende,
but it may be distinguished by picking with a needle which
will cause the thin, characteristic flakes to exfoliate.
OLIVINE. This mineral is a compound of silica with iron
and magnesia; it forms crystals of the rhombic type. The
physical properties are very similar to those of pyroxene and
hornblende. The colour is greenish and generally lighter than
in these two minerals, and the absence of the characteristic
cleavage is of value as a means of determination.
Olivine occurs more particularly in the very dark-coloured
igneous rocks.
II. NON-ESSENTIAL AND SECONDARY MINERALS OF
IGNEOUS ROCKS
The great mass of igneous rocks is made up of the minerals
given above ; other important minerals occur in less amount
as wrell as some which may or may not be present in a given
rock and, therefore, are non-essential. As a result of decay
and alteration new minerals may be formed : these are usually
called secondary.
The commonest non-essential and secondary minerals of
igneous rocks are:
MINERALS AND ROCKS 13
GARNET GROUP. Garnets are compounds of silica with
alumina, iron, lime, and sometimes with manganese, chromium,
etc. They form crystals of the regular or cubic type which
are often symmetrically twelve-sided forms, each face being
a rhombus.
The lustre is vitreous to resinous; the colour varies with
the composition, usually being reddish or brownish, but some-
times green; the streak is colourless; the hardness is 6-5 to 7-5 ;
and the specific gravity 3-15 to 4-3.
Garnet is more common in metamorphic than in igneous
rocks. Common varieties are useful as abrasives on account
of their hardness and toughness; clear and pure varieties,
particularly the red pyrope, are used as gem stones.
CHLORITE. This mineral occurs only as the result of the
decay of other minerals such as augite, hornblende, and mica.
It is of complicated composition, soft, and greenish in colour.
Chlorite belongs more properly to the metamorphic rocks, but
it may occur in igneous rocks which are but little altered.
In addition to the above minerals a long list might be made
of the non-essential minerals of the igneous rocks. Some of
these will be described under different heads, e.g., magnetite,
hematite, pyrite, and apatite.
III. ADDITIONAL MINERALS OF THE METAMORPHIC
ROCKS
Igneous rocks which have been subjected to extreme alter-
ation frequently contain minerals not present before the
changes were effected. Chlorite and garnet, already men-
tioned, are among the commonest of these, and in addition
are the following :
SERPENTINE. This mineral is essentially a compound of
silica, magnesia, and water. It is questionable if it has a
crystal form of its own as it always occurs as an alteration
of hornblende, pyroxene, olivine, etc.
The lustre is resinous to greasy; the colour generally
greenish to 3^ellowish green; the streak colourless; the hard-
ness variable but generally low, about 2-5 to 4; the specific
gravity 2*5 to 2-65.
The dark-coloured igneous rocks, particularly those made
14 ELEMENTARY GEOLOGY
up of a large percentage of olivine, are liable to be altered
en masse into serpentine. Sometimes this massive serpentine
is of value as decorative stone, as in the Gaspe peninsula and
in the eastern townships of Quebec.
Serpentine sometimes assumes a delicately fibrous form
known as chrysotile which is commonly called asbestos. The
fire-resisting properties of this material and its capability
of being woven into fireproof fabric give it a high value.
The mining of asbestos is one of the unique industries of
Canada; it centres chiefly about Black Lake in the eastern
townships of Quebec.
TALC. This is another compound of silica, magnesia, and
water which results from the alteration of minerals like
hornblende, pyroxene, and olivine. When pure the lustre is
pearly, the colour white or greenish, and the streak colourless.
It is one of the softest minerals known, as the hardness ranges
from less than i to 1-5.
Clean, well-crystallised talc is not common and is of value
for the manufacture of toilet powders, for which purpose it is
extensively mined near Madoc in Ontario. Impure massive
forms of talc are known as soapstone and are used for various
industrial purposes.
SILLIMANITE. Essentially a compound of silica and alumina.
It forms long slender crystals which in extreme cases are
fibrous. The lustre is non-metallic; the colour brown, grey,
or green; the streak uncoloured; the hardness 6 to 7; and
the specific gravity 3-2 to 3-3.
This mineral would scarcely be mentioned were it not for
its presence in rocks of frequent occurrence in northern Canada.
EPIDOTE. This mineral is a complicated compound of silica,
alumina, iron, and lime with a small amount of water; it
occurs in both igneous and metamorphic rocks. The crystal
form is monoclinic.
The lustre is vitreous to pearly and resinous; the colour
usually yellowish green ; the streak uncoloured ; the hardness
6 to 7; and the specific gravity 3-25 to 3-5.
SERICITE. This mineral is related to the micas, but it con-
tains more water than the typical micas already mentioned.
It occurs in the form of silvery, glistening scales in schistose
rocks and is always the result of alteration of original minerals.
MINERALS AND ROCKS 15
IV. MINERALS OF THE SEDIMENTARY ROCKS
Rocks which have been laid down in water may contain
fragments of any of the minerals of the igneous rocks; in
addition are the following:
CALCITE. Carbonic acid gas is a constituent of the atmo-
sphere ; it is a compound of oxygen and carbon and is formed
when fuel is burned either in the ordinary way or in the
lungs of animals. This gas is always ready to enter into
combination with lime, as may be proved by blowing air
from the lungs into lime water. On performing this simple
experiment one will immediately see a white powder formed
which settles to the bottom of the vessel. This white powder
is carbonate of lime. The same substance occurring under
natural conditions where it has a chance to crystallise is the
mineral calcite.
Crystals of calcite are usually six-sided prisms with pointed
ends; frequently also, especially in rocks, the form is that of
a rhombohedron. Whatever the shape of the crystal the
cleavage is rhombohedral, a property which is well developed
and constantly present.
The lustre is non-metallic, vitreous to earthy; the colour
is normally clear transparent, but opaque white and various
lightly coloured varieties are known; streak colourless; hard-
ness 2-5 to 3-5; specific gravity about 27.
Pure limestone is composed entirely of carbonate of lime,
probably in the form of calcite. Marble is distinctly crystalline
limestone, and therefore is certainly made up of the mineral
calcite. Calcite is of frequent occurrence in mineral veins and
is often the result of decay in lime-bearing minerals of the
igneous rocks.
Carbonate of lime sometimes crystallises in a form different
from that of calcite; it is then known as aragonile, which
is a distinct mineral although of the same composition
as calcite.
MAGNESITE. Just as calcite is the carbonate of lime, mag-
nesite is the carbonate of magnesia. The physical properties
are somewhat similar, but magnesite is heavier, having a
specific gravity usually exceeding 3. This mineral is included
here on account of its close relationship to calcite rather than
16 ELEMENTARY GEOLOGY
to its occurrence in stratified rocks ; its more usual occurrence
is as an alteration product in connection with serpentine.
DOLOMITE. This mineral is a carbonate of lime and mag-
nesia; it is intermediate between calcite and magnesite, and
has physical properties in accord with that position. The
significance of this mineral will be more fully appreciated
when the description of the sedimentary rocks has been read.
KAOLINITE. This is a very important mineral composed of
silica, alumina, and water. The form of the crystal is doubtful
as the mineral usually occurs as tiny pearly scales. The lustre
is non-metallic pearly; the colour is normally white, but
various light tints may be shown; streak uncoloured; hard-
ness i to 2-5; specific gravity about 2-5.
Kaolinite results from the decay of orthoclase. Together
with other related minerals it makes up the bulk of clay beds
and is responsible for the plastic properties of clay.
V. MINERALS USED AS ORES OF THE METALS
Gold is found chiefly in the native state, but it also occurs
as a constituent of a few rare minerals. The metal is also
obtained from the ores of copper and other metals in which
it occurs in small quantities.
NATIVE GOLD. Gold crystallises in the regular system
usually in the form of octahedrons. The lustre is metallic;
colour and streak yellow; hardness 2-5 to 3; specific gravity
15-6 to 19-5; malleable.
Silver occurs native and in combination with other sub-
stances in a number of minerals. Much silver is produced
also from lead ores in which silver takes the place of part of
the lead.
NATIVE SILVER. The crystals belong to the cubic system,
but generally they are aggregated into dendritic masses. The
lustre is metallic ; the colour and streak silver white ; hardness
2-5 to 3; specific gravity 10-1 to n-i; malleable.
ARGENTITE. This mineral is a compound of silver and
sulphur which crystallises in the cubic system. Lustre metallic ;
colour and streak blackish lead-grey; hardness 2 to 2-5;
specific gravity about 7-3; somewhat malleable.
Copper occurs native and also in combination with other
MINERALS AND ROCKS 17
elements in a large number of minerals. The chief ores are
as follows:
NATIVE COPPER. Crystallisation cubic, but generally shows
dendritic aggregations; lustre metallic; colour copper-red;
streak metallic shining; hardness 2-5 to 3; specific gravity
8-8; malleable.
CHALCOPYRITE. Also called copper pyrites. This mineral is
a compound of copper, iron, and sulphur; crystals tetragonal;
lustre metallic; colour brass-yellow; streak greenish black;
hardness 3-5 to 4; specific gravity 4-1 to 4-3; brittle.
BORNITE. Also called purple copper ore. Bornite is a com-
pound of copper, iron, and sulphur differing in proportion from
that of chalcopyrite ; it crystallises in the cubic system. The
lustre is metallic; the colour between red and brown; streak
greyish black ; hardness 3; specific gravity 4-4 to 5-5; brittle.
CHALCOCITE. Also known as copper glance. This mineral is
a compound of copper and sulphur; its crystals belong to
the rhombic system. The lustre is metallic; the colour and
streak blackish lead-grey; hardness 2-5 to 3; specific gravity
5-5 to 5-8; brittle.
MALACHITE. A carbonate of copper with water; crystals
monoclinic. The lustre is adamantine to vitreous; the colour
bright green; streak paler green; hardness 3-5 to 4; specific
gravity 3-7 to 4-01.
In addition to being used as an ore of copper, malachite is
a very handsome decorative material.
Iron in the native condition is very rare. The important
minerals are the oxides and carbonates of iron.
HEMATITE. Sometimes called red iron ore. A compound of
iron and oxygen with 70 per cent, iron; crystals hexagonal;
lustre metallic; colour dark steel-grey; streak red to brown;
hardness 5-5 to 6-5; specific gravity 4-5 to 5-3; brittle.
MAGNETITE. Also known as magnetic iron ore. A compound
of iron and oxygen with 72-4 per cent, iron; crystals cubic,
generally octahedra ; lustre metallic ; colour and streak black ;
hardness 5-5 to 6-5; specific gravity 4-9 to 5-2; brittle; mag-
netic. The colour of the streak and the property of magnetism
suffice to distinguish this mineral from hematite.
LIMONITE. Known also as brown iron ore. A compound of
B
i8 ELEMENTARY GEOLOGY
iron, oxygen, and water; no crystallisation; lustre sub-
metallic, silky; colour brown; streak yellowish brown;
hardness 5 to 5-5; specific gravity 3-6 to 4; brittle.
SIDERITE. A compound of iron and carbonic acid; crystal-
lises in rhombohedrons of the hexagonal system; lustre non-
metallic; colour variable, but usually ash-grey to brownish;
streak uncoloured; hardness 3-5 to 4-5; specific gravity 37
to 3-9; brittle.
The chief ore of lead and the only one to be considered
here is galena, which is also important as a source of silver,
as the lead is frequently replaced in part by silver.
GALENA. A compound of lead and sulphur with 86-6 per
cent. lead. Crystals cubic; cleavage cubic; lustre metallic;
colour and streak lead-grey; hardness 2-5 to 275; specific
gravity 7-25 to 77; brittle.
Zinc is obtained from various minerals, chiefly the sulphide,
carbonate, and silicate ; the first mentioned is much the most
important and will alone be considered.
SPHALERITE. Also known as zinc blende. A compound of
zinc and sulphur with 67 per cent, zinc; crystals cubic with
pronounced cleavage; lustre resinous; colour variable, brown,
yellow, black, red, green, commonly amber-coloured; streak
white to light reddish brown ; hardness 3-5 to 4 ; specific gravity
3-9 to 4-2; brittle.
Cobalt occurs in a number of rather rare minerals. On
account of its abundance in the silver region of Cobalt in
Ontario, we may regard smaltite as the most important.
SMALTITE. A compound of cobalt and arsenic with usually
a small amount of iron and nickel; crystals cubic; lustre
metallic ; colour tin-white to steel-grey ; streak greyish black ;
hardness 5-5 to 6; specific gravity 6-4 to 7-2; brittle.
Nickel occurs in several minerals, the chief of which are
compounds of nickel with sulphur, arsenic, or antimony.
Nevertheless, most of the nickel from the famous mines at
Sudbury, Ontario, is obtained from a compound of iron and
sulphur known as pyrrhotite which is mixed with a nickel-
iferous mineral, pentlandite. Visible pentlandite is of rather
MINERALS AND ROCKS 19
rare occurrence in these ores, consequently the more common
mineral pyrrhotite will be described.
PYRRHOTITE. A compound of iron and sulphur; crystals
hexagonal, rare; lustre metallic; colour bronze-yellow to
copper-red; streak dark greenish black; hardness 3*5 to 4*5;
specific gravity 4-4 to 4-68; brittle.
This mineral somewhat resembles another compound of
iron and sulphur, pyrite, but it may be distinguished by its
inferior hardness and the difference in colour and streak.
Arsenic occurs as native arsenic and in combination with
many of the metals. Most of the arsenic of commerce is
produced as a by-product in treating ores for other metals.
ARSENOPYRITE, ARSENICAL PYRITES, OR MISPICKEL. A
compound of iron arsenic and sulphur with 46 per cent, arsenic ;
crystals rhombic ; lustre metallic ; colour silver-white to steel-
grey; streak dark greyish black; hardness 5-5 to 6; specific
gravity 6 to 6-4; brittle.
Antimony occurs native and in combination with many
metals; the chief ore is stibnite.
STIBNITE. This mineral, also known as antimony glance, is
a compound of antimony and sulphur with 71-8 per cent,
antimony. The crystals belong to the rhombic system and
are often very elongated; lustre metallic; colour and streak
lead-grey; hardness 2; specific gravity 4-5 ; sectile.
Tin is obtained almost entirely from one mineral, cassiterite.
CASSITERITE OR TIN STONE. A compound of tin and oxygen.
The crystals are frequently well formed and belong to the
tetragonal system; lustre non-metallic, adamantine; colour
usually brown to black, but sometimes even white; streak
colourless, greyish, brownish; hardness 67; specific gravity
6-4 to 7-1; brittle.
VI. OTHER MINERALS OF ECONOMIC IMPORTANCE
GYPSUM. A compound of lime, sulphuric acid, and water;
it is sulphate of calcium with 20-9 per cent, water. The crystals
are frequently well formed and belong to the monoclinic
system; the cleavage is well marked; lustre non-metallic,
pearly, shiny, sub- vitreous ; colour normally white, sometimes
20 ELEMENTARY GEOLOGY
greyish, reddish, etc.; streak white; hardness 1-5 to 2;
specific gravity 2-3.
Pure, well-crystallised gypsum is colourless and trans-
parent; it is known as selenite. Massive, granular, scaly,
and other varieties are known. Plaster of Paris is manufac-
tured by heating gypsum until most of the water is expelled.
The setting of the plaster is due to the taking up of water
and the re-formation of crystallised gypsum. As gypsum occurs
chiefly in beds with other stratified rocks it might well be
considered as one of the minerals of the stratified rocks.
HALITE OR COMMON SALT. A compound of sodium and chlor-
ine. Crystals cubic with good cubic cleavage; lustre vitreous;
colour usually white, but may be reddish, greyish, etc. ; streak
white; hardness 2-5; specific gravity 2-1; brittle; soluble in
water; saline taste. Like gypsum, rock salt may be con-
sidered as one of the minerals of the stratified rocks.
CORUNDUM. A compound of aluminium and oxygen, i.e.
alumina. The crystals belong to the hexagonal system
and are frequently well formed; lustre non-metallic, vitre-
ous ; colour extremely variable, white, red, blue, brown,
yellow ; streak colourless; hardness very high, 9 ; specific
gravity 4 ; brittle.
On account of its hardness corundum is a valuable abrasive.
The impure black variety is emery. Some of the most valuable
jewels are corundum; for instance, the oriental ruby is red
corundum, and the oriental sapphire is blue corundum.
GRAPHITE. This mineral is carbon in the form which is
commonly known as blacklead. Lustre metallic; colour and
streak black; hardness i to 2; specific gravity 2-2; sectile;
marks paper.
Graphite is used for making black paint and stove polish,
for lead pencils and crucibles; it also finds many other appli-
cations in the industrial arts. Occurrences of graphite are
common in eastern Ontario and in Quebec north of the
Ottawa river.
PYRITE. A compound of iron and sulphur with 53-3 per
cent, sulphur. The crystals are cubes or modified cubes;
lustre metallic; colour pale brass-yellow; streak greenish or
brownish black; hardness 6 to 6-5 ; specific gravity 4-8 to 5-2 ;
brittle. Pyrite is a very common mineral; it occurs in veins,
MINERALS AND ROCKS 21
as an accessory constituent in igneous rocks, also in meta-
morphic and sedimentary rocks.
The chief use of pyrite is for the manufacture of sulphuric
acid: it is not commonly employed for making iron as the
entire separation of the sulphur is too difficult. Pyrite fre-
quent^ carries small amounts of gold, in which case it is used
as an ore of that metal. The resemblance of pyrite to gold
has led to the popular name "fool's gold."
APATITE. A compound of lime, phosphoric acid, and
fluorine. Crystals hexagonal, often with well-developed six-
sided prisms; lustre vitreous to resinous; colour usually
greenish, sometimes reddish or otherwise tinted; streak
colourless; hardness 5; specific gravity about 3; brittle.
This mineral is important as a source of phosphorus and
phosphoric acid; it occurs in eastern Ontario and in Quebec
north of the Ottawa river.
AGATE. Water containing silica in solution sometimes
deposits that substance on the walls of cavities in certain of
the igneous rocks. Eventually the cavity is wholly or par-
tially filled with silica, arranged in a concentric manner and
presenting delicate and varying shades of colour. Silica in
this form is known as agate.
JASPER. This mineral is also a form of silica to which a
bright red colour is given by the presence of oxide of iron.
CHROMITE. Also known as chromic iron ore. A compound
of iron, chromium, and oxygen. Crystals cubic system; lustre
sub-metallic; colour iron-black or brownish black; streak
brown; hardness 5-5; specific gravity about 4-4; brittle.
Chromite is smelted with iron ores to produce an alloy of
chromium and iron; the mineral, therefore, might be con-
sidered as an ore of these metals. A great amount of chromite.is
used for making various chemical compounds much employed
in the industrial arts.
ROCKS
Rocks are masses of mineral matter of sufficient size and
importance to form essential elements in the building up of
the earth's crust: they are to be distinguished from those
smaller, less frequent, and non-essential occurrences of mineral
22 ELEMENTARY GEOLOGY
matter, such as the filling of veins and cavities. Rocks are
composed of mineral matter, but not always of definite
minerals. Sometimes a rock is made up of one mineral only,
as in the case of pure marble which is composed entirely of
the mineral calcite; or in the case of anorthosite made up
entirely of the mineral feldspar. Other rocks are composed
of several minerals; for instance, the rock granite is made
up of the minerals quartz, feldspar, and mica. Rocks such
as sandstone are not made of definite minerals, but of broken
pieces of minerals derived from the decay of earlier rocks
and cemented together by a foreign substance; such rocks
are termed fragmented or clastic.
The broadest classification of rocks is based on their mode
of origin as follows:
1. Igneous rocks. The result of the solidification of molten
matter.
2. Sedimentary rocks. Built up of mineral matter derived
from earlier rocks and deposited in layers, usually by
water but sometimes by air.
3. Metamorphic rocks. Rocks of either of the above classes
which have been so altered by natural processes that
their original nature is greatly changed.
IGNEOUS ROCKS
Molten matter from the interior of the earth may be poured
out on the surface, or it may rise into fissures and consolidate
before escaping, or it may cool at great depths in the earth.
and not be visible until the overlying rocks have been worn
away by erosion. The nature of the resulting igneous rock
depends in part on the manner of cooling as above indicated,,
and in part on the original chemical composition of the
molten matter. The manner of cooling expresses itself in the
structure of the rock, and the original chemical composition is
indicated by the minerals which form in the process of cooling.
All igneous rocks, therefore, have to be examined from two
points of view — the structure and the mineral composition.
If a molten mass is poured out on the surface of the earth
(extrusive) it will cool with comparative rapidity, and the
chemical substances will not have time to gather together
MINERALS AND ROCKS 23
and crystallise into minerals, or at least this process will not
be complete, with the result that more or less uncrystallised
material, glass, will be present. If the flow is thin and quickly
cooled the whole mass may be glass, and less glass and more
crystals will result the thicker the flow and the slower the
rate of cooling. Rocks of this type are volcanic. On the other
hand, if the molten mass cools very slowly deep down in the
earth there is ample time for the whole of the matter to
crystallise, resulting in an even-grained rock composed entirely
of minerals without the least trace of glass. Such rocks are
plutonic, and they are said to have a granitic structure, not
PIG. 6. GRANITE, ILLUSTRATING THE "GRANITIC" OR EVEN-GRAINED
STRUCTURE OF DEEP-SEATED IGNEOUS ROCKS
The light mineral is orthoclase, and the very dark mineral is black mica. The intermediate
or greyish mineral is quartz, which appears dark in a photograph by reason of its
transparency.
because they are necessarily granite, but because they have
the even-grained structure seen in that familiar rock. Between
the conditions which give rise to volcanic and plutonic rocks
there are evidently intermediate ones in which the molten
matter fills cracks in the earth or otherwise occupies positions
intermediate between the two extremes. Such rocks are likely
to present porphyrilic structure in which some of the minerals
are very large and the others form a fine-grained ground mass.
Masses of molten rock (magmas) vary greatly in their chemical
composition: those in which there is more than about 50 per
cent, silica are commonly called acid, and those in which the
silica is less than 50 per cent, basic. On crystallising, an
acid magma is likely to form a rock containing quartz and
ELEMENTARY GEOLOGY
orthoclase feldspar and presenting a light colour; on the
other hand, a basic magma will form a dark-coloured rock
with plagioclase feldspar and much hornblende or pyroxene.
Closely related to the igneous rocks, but not formed directly
by the solidification of magmas, are the accumulations of fine-
grained debris from volcanoes, tuffs, and the coarser accumu-
lations in which angular fragments are visible, volcanic breccias.
The chemical composition of igneous magmas is so variable,
and the manner of cooling so diversified, chat the resulting
igneous rocks are not to be regarded like minerals, i.e. as
definite compounds of fixed composition, but rather as a
series of consolidated magmas showing all transitions in
chemical and mineralogical composition and in structure
from one end of the chain to the other. The following table,
which indicates the commonest igneous rocks, is not to be
regarded as a rigid classification, but as an orderly arrange-
ment of a few typical rocks between which many transitional
stages occur.
CLASSIFICATION OF TYPICAL IGNEOUS ROCKS
(Modified from Kemp)
ACID
EXCESS OF LIGHT-COLOURED MINERALS
BASIC
EXCESS OF DARK-COLOURED MINERALS
Glassy
structure;
volcanic
origin
Cbsidian
Andesite obsidian
Basalt
Obsidian
Chief feldspar orthoclase
Chief feldspar plagioclase
No feldspar
With
quartz
Without
quartz
With
nepheline
With biotitc or
hornblende or
both
With
pyroxene
Vesicular,
glassy or
fine-grained
structure;
volcanic
origin
Rhyolite
Trachyte
Andesite
Basalt
Augitite
Porphyritic
structure;
intrusive or
dike origin
Quartz
porphyry
Granite
porphyry
Trachyte
porphyry
Syenite
porphyry
Andesite
porphyry
Diorite
porphyry
Basalt
porphyry
Gabbro
porphyry
Pyroxenite
porphyry
Pendotite
porphyry
Granitic
structure ;
plu tonic
origin
Granite
Syenite
Nepheline
syenite
Diorite
Gabbro
Diabase
Norite
Pyroxenite
Peridotite
Fragmental
Rhyolite
tuffs and
breccias
Trachyte
tuffs and
breccias
Andesite tuffs
and breccias
Basalt tuffs and
breccias
MINERALS AND ROCKS 25
A careful analysis of this table will save the student much
mere memory work in acquiring a knowledge of igneous rocks.
The horizontal columns indicate rocks of similar structure,
while the vertical columns indicate rocks of similar chemical
and mineralogical composition.
After having considered the obsidians we will take up the
rocks according to their arrangement in vertical columns.
We thus have series or groups of rocks similar in chemical
and mineralogical composition but differing in structure and
mode of origin. These groups may conveniently be desig-
nated by names compounded of the first and last repre-
sentative, thus " rhyolite-granite series."
OBSIDIAN. The characteristic feature of obsidian is its
glassy structure. Typical examples look like a piece of dark
green or brownish bottle glass. According to chemical com-
position obsidians range from the acid type, obsidian proper,
through andesite obsidian to the basic, basalt obsidian.
Incipient crystals may be present and the rock may be
more or less filled with bubbles: pumice is an extremely
bubbly or vesicular volcanic glass.
Rhyolite-granite series.
RHYOLITE. This is a volcanic rock of light colour and very
fine-grained (felsitic) structure. It is made up of a large
amount of orthoclase, usually a little plagioclase, quartz, and
a less amount of the dark minerals which may be biotite,
hornblende, or pyroxene. Bubbles are sometimes present as
in most volcanic rocks.
QUARTZ PORPHYRY. This rock, sometimes called rhyolite
porphyry, is of the same chemical and mineralogical com-
position as rhyolite: it differs, however, in that some of the
quartz and orthoclase crystals are much larger than the
finer grained minerals that make up the rock mass; in other
words, the structure is porphyritic. The rock occurs in dikes,
in intrusive sills, and even in the thicker flows of lava. Unlike
the volcanic rocks, quartz porphyry is free from bubbles.
GRANITE PORPHYRY. This rock resembles quartz porphyry
in the development of large crystals of quartz and orthoclase;
it differs in that the groundmass is not fine-grained as in
quartz porphyry, but made up of crystals of fair size. The
26 ELEMENTARY GEOLOGY
rock is simply a granite in which certain crystals reach por-
phyritic dimensions.
GRANITE. This is the deep-seated or plutonic representative
of the rhyolites and quartz porphyries: it is distinguished by
the fairly coarse and even grain of all the constituent minerals.
Many varieties of granite are known according to the develop-
ment of the dark-coloured minerals. The most typical granite
is made up of quartz, orthoclase, and muscovite; by a replace-
ment of the muscovite by other minerals we have biotite
granite, hornblende granite, etc.
GRANODIORITE. Rocks intermediate in composition between
granite and diorite are of common occurrence; they are
characterised by the presence of both kinds of feldspar.
Typical granodiorite is a rock of granitic structure and
appearance composed of quartz, orthoclase, plagioclase, and
one or more of the dark-coloured minerals, hornblende and
biotite. Many of the so-called granites of Canada are really
granodiorites. This rock does not fall into the classification
given in the table : it is but one example of the many inter-
mediate types which exist.
RHYOLITE TUFFS AND BRECCIAS. Fragmental rocks formed
of volcanic debris having the chemical composition of the
rhyolite-granite series. The types of finer grain are tuffs, and
those showing angular fragments are breccias.
Trachyte-syenite series.
TRACHYTE. This is the volcanic representative of a group
of rocks characterised by preponderating orthoclase feldspar
and no quartz: it may be called a quartzless rhyolite. The
structure is felsitic and bubbles may be present as in rhyolite.
TRACHYTE PORPHYRY. A trachyte groundmass with por-
phyritic crystals of orthoclase. The intrusive or dike
representative of the series.
SYENITE PORPHYRY. A groundmass of fair-sized and even-
grained orthoclase and mica or hornblende with porphyritic
crystals of orthoclase.
SYENITE. The plutonic representative of the series. The
rock is composed of fair-sized, even-grained orthoclase and
mica or hornblende or both: it is simply a quartzless granite.
MINERALS AND ROCKS 27
Syenite is popularly confused with granite, but it may easily
be distinguished by the absence of quartz.
TRACHYTE TUFFS AND BRECCIAS. The fragmental repre-
sentatives of the trachyte-syenite series.
NEPHELINE SYENITE. Syenite in which the orthoclase is in
part replaced by nepheline. Nepheline-bearing rocks corre-
sponding to the other members of the series are known, but
they are of less importance to the beginner.
Andesite-diorite series.
ANDESITE. This rock is the volcanic representative of a
series of intermediate chemical composition which gives rise
to preponderating feldspar of the plagioclase type and to
hornblende as the most typical of the dark-coloured minerals.
As in composition, the rocks of the group are intermediate in
colour between the light rocks like granite and syenite and the
dark basic rocks of the last two columns of the table. The
structure of andesite is felsitic, as in rhyolite and trachyte,
but the colour is somewhat darker. The mineral components
are typically plagioclase and hornblende or biotite: when
quartz is present the rock is called dacite, and when pyroxene
is present it is cwgite andesite.
ANDESITE PORPHYRY. The dike representative of the series.
It. resembles andesite in chemical and mineralogical composi-
tion, but has porphyritic crystals of plagioclase.
DIORITE PORPHYRY. Like andesite porphyry, but the
groundmass is no longer felsitic but composed of crystals
of fair size.
DIORITE. The plutonic representative of the series: it is
composed of fairly large and even-sized crystals of plagioclase
and hornblende. The rock is hard and tough, usually greenish
in colour, and darker than the corresponding granites and
granodiorites. In mica diorite the hornblende is replaced
wholly or in part by biotite.
ANDESITE TUFFS AND BRECCIAS. Fragmental rocks composed
of volcanic debris having the general composition of andesite.
Basalt-gabbro series.
BASALT. This is a very common rock of volcanic origin
and more basic composition than those already mentioned.
28 ELEMENTARY GEOLOGY
The structure is felsitic but some glass may be present. In
mineral composition it differs from andesite by the replace-
ment of hornblende by pyroxene. Olivine is frequently
present as well as grains of magnetite. The structure is often
cellular and rough; sometimes the cavities are large and are
known as amygdaloids on account of their almond-like shape.
Basalt is a heavy, dark- coloured, variable, and rough type
of stone.
BASALT PORPHYRY. Basalt with porphyritic crystals of
augite and frequently also of olivine.
GABBRO PORPHYRY. A rock of the chemical and mineral
composition of basalt, but with porphyritic crystals of pyroxene
or olivine imbedded in a groundmass of plagioclase and
pyroxene of fair size.
GABBRO. This is a dark-coloured, heavy, and massive rock
composed of even-grained and fairly large crystals of plagio-
clase and pyroxene. In structure it is comparable with the
granites, syenites, and diorites. Gabbro in which the ordinary
pyroxene is replaced by the rhombic variety, hypersthene, is
known as norite.
DIABASE. In mineral composition this rock is the same as
gabbro, but in texture it is intermediate between gabbro and
basalt. The feldspar crystals are much elongated and seem
to have crystallised first, as the pyroxene fills in the spaces
between the lath-like plagioclase crystals. By the naked eye
diabase can usually be distinguished from gabbro by the
reflections from the elongated feldspar crystals on freshly
broken surfaces.
Augitite-peridotite series.
AUGITITE. This is a rather rare rock resembling basalt to
the naked eye. On close examination, however, it is seen to
contain no feldspar and to consist essentially of augite em-
bedded in a glassy groundmass.
PYROXENITE. A heavy, ultra-basic, dark-coloured rock
consisting essentially of fair-sized, even-grained crystals of
pyroxene.
PERIDOTITE. Resembles pyroxenite but contains also olivine.
PYROXENITE AND PERIDOTITE PORPHYRIES. Pyroxenites
and peridotites in which porphyritic crystals are developed.
MINERALS AND ROCKS 29
BASALT TUFFS AND BRECCIAS. The fragmental volcanic
rocks of basic composition are generally referred to by this
name as the exact texture and mineral composition are hard
to determine.
SEDIMENTARY ROCKS
In another chapter will be found an account of the manner
in which the debris derived from the decay of pre-existing
rocks is spread out by water, and in some cases by wind or
other agency, to form the sedimentary or stratified rocks.
The present chapter deals only with the naming and classi-
fication of rocks of this kind.
The stratified rocks may be classified as follows:
1. Mechanical sediments:
(a) Undecomposed fragments of earlier rocks.
(b) Chemically altered residues of earlier rocks.
2. Rocks formed by organic agencies.
3. Chemical precipitates from solution.
la. When a rock is broken up by the action of natural
forces, the fragments may be carried into the sea and laid
down in beds. At first these beds are soft and incoherent, but
eventually they become hardened; in either condition they
are rocks in the geological use of that term. The hardening
may result from mere pressure, but generally it is caused by
the setting of some cementing matter around the fragments.
Three types are recognised according to the size and shape of
the fragments — breccia, conglomerate, and sandstone.
BRECCIA. This rock is made up of angular fragments of
earlier rocks cemented by some foreign matter — clay, lime,
silica, or other substance. Breccias are formed near to
the point of origin of the fragments which have not been
rounded by transportation. These rocks are sometimes
named in accord with the nature of the fragments, thus
limestone breccia, granite breccia, etc. They are also named
in accord with their method of origin, as talus breccia
formed at the foot of a cliff, friction breccia formed by the
rubbing together of rocks in earth movements. We have
already seen that angular volcanic fragments cemented
into a rock also form breccias.
ELEMENTARY GEOLOGY
CONGLOMERATE. Beds of gravel cemented into solid rock
in the same manner as in the case of breccia become con-
glomerates or "pudding stones." These differ from breccias
only in the rounding of the component fragments. This con-
dition indicates that the fragments have been subjected
to the action of currents, or waves, or ice, and that they
did not of necessity originate in the locality in which they
are found.
Conglomerates are usually named from the character of
the component fragments of rock; for instance, jasper con-
glomerate is a very handsome decorative rock composed of
^Jilyii
FIG. 7. JASPER CONGLOMERATE
The rounded dark fragments are bright red jasper; the groundmass is chiefly quartz.
rounded fragments of red jasper cemented by silica. Fre-
quently the component pebbles are of a nature so varied that
it is impossible to name the rock on this basis. Conglomerates
of glacial origin, with ice-worn pebbles embedded in a clay
matrix, are known as tillites.
SANDSTONE. Sand is made up of the finer fragments derived
from earlier rocks. In most cases the breaking up of the
original rock has been so complete that each grain of sand is
a fragment of a distinct mineral. Naturally the more resistant
minerals have better survived the processes of decay; in con-
sequence, the hard mineral, quartz, is of most frequent
occurrence in sand beds; but feldspar, garnet, magnetite,
mica, and other minerals of the igneous rocks are by no
means absent. In the coarser sands, fragments of rock
MINERALS AND ROCKS 3*
matter not reduced to individual minerals are often to
be observed.
Beds of sand become hardened into sandstones, chiefly by
the setting of cementing matter between the grains. The
commonest cements are clay, silica, lime, and the oxides of
iron. The character of the cement is made use of to give a
name to the sandstone; thus we have clayey or argillaceous
sandstones, siliceous sandstones, calcareous sandstones, and
ferruginous sandstones. It is obvious that the amount of
cement may increase until it exceeds that of the constituent
grains; for instance, an argillaceous sandstone by an increase
of clay becomes an arenaceous or sandy shale, and a cal-
careous sandstone by an increase of lime passes gradually
into an arenaceous limestone.
Sand is used largely in building operations, in glass-making,
and in making hearths for furnaces : for the first purpose the
greater the proportion of quartz grains the better;' for the
last two purposes a very high proportion of quartz is essential.
Sandstones are used very extensively for building: varieties
which may be chiselled with facility are called freestone.
Sandstones in which the constituent grains are fine and sharp
and with just the right degree of cohesion are used for the
manufacture of grindstones and scythe-stones.
1 6. CLAY AND SHALE. The decay of orthoclase feldspar
in the igneous rocks gives rise to a new mineral, kaolinite, a
soft, plastic, insoluble substance, that is washed down by the
rivers and deposited in the sea together with a varying amount
of fine sand to build up beds of clay. Pure kaolinite is scarcely
known as a stratified rock: clay is composed of kaolinite or
related minerals with varying amounts of other substances,
chiefly fine sand and carbonate of lime. Hardened clay is
known as shale.
Clay is one of the most useful substances known to man;
in consequence.it has received much study and an extensive
classification has arisen. Different varieties of clay are suited
to various industrial purposes — from the making of common
brick and tile to the manufacture of the finest grades of
porcelain. The fire-resisting properties of certain clays render
them extremely valuable for lining furnaces.
2. LIMESTONE. Carbonate of lime, derived originally from
32 ELEMENTARY GEOLOGY
the decay of igneous rocks, is carried in solution by the rivers
and added to the water of the ocean. The inhabitants of the
sea make use of this lime to construct shells or other hard
parts. On the death of the organism these shells accumulate
on the floor of the sea and build up beds of limestone. In
many cases the character of the shells may easily be deter-
mined, and limestones are sometimes named from the
prevailing organism present; thus encrinal limestone, largely
made up of the remains of encrinites, coralline limestone,
etc. In other cases, the shells have been so ground up by wave
action or currents that they are no longer recognisable as such.
Further, a process of solution and re-precipitation in the
slimes on the sea floor, and a development of fine crystalline
structure, entirely masks the organic origin of the stone.
By an admixture of clay pure limestone becomes argilla-
ceous limestone, and with a greater amount of clay it becomes
calcareous shale. Similarly by an increasing admixture of
sand, limestones pass into arenaceous limestones and calcareous
sandstones.
In a chemical way also, limestones are subject to much
variation, chiefly by the replacement of part of the lime by
magnesia. When the magnesia is 5 per cent, or somewhat
more, the rock is called magnesian limestone; a still greater
amount of magnesia constitutes it a dolomitic limestone; and
when the magnesia approaches 2172 per cent, (the percentage
in the mineral dolomite) the rock is called dolomite. A similar
series of varieties is caused by the replacement of carbonate
of lime by carbonate of iron.
INFUSORIAL EARTH. Organisms which secrete a siliceous
skeleton may also build up layers of rock or furnish the
material for flints, cherty nodules, or disseminated silica in
other stratified rocks. The only important rock of this kind
is infusorial earth which is made up of the remains of minute
siliceous organisms. This material is of use as an abrading
and polishing substance: it is obtained in large quantity near
Windsor, Nova Scotia.
COAL. Coal being composed of the remains of plants
belongs properly to the category of organic rocks.
3. GYPSUM. This mineral is soluble and is a constant
constituent of the waters of the ocean; if, under prevailing
MINERALS AND ROCKS 33
desert conditions, a portion of the sea is cut off from the
open ocean, evaporation of the water results in the deposition
of beds of gypsum.
ROCK SALT. Beds of rock salt are formed in the same
manner as those of gypsum.
IRON ORES. Certain types of iron ore, particularly bog iron
ore, have been formed in beds by the precipitation of iron
from solution in water.
METAMORPHIC ROCKS
Both sedimentary and igneous rocks may be so altered by
the effect of heat and terrestrial strains that they lose much
of their original appearance and acquire new properties,
chemical, mineralogical, or structural; in some cases they
differ so greatly from the rocks that gave rise to them that
their origin may remain conjectural only. Such rocks are said
to have been metamorphosed and they are referred to as the
metamorphic rocks.
The subject of metamorphism is a large one and is briefly
treated in another chapter. We shall consider here only the
rocks themselves without regard to the details of their origin.
GNEISS. In the narrower sense this name is given to rock,
originally granite, which has acquired a banded or laminated
structure as the result of metamorphism. Instead of the
mineral components being uniformly distributed as in granite,
they are rolled out into more or less distinct laminae, with the
result that the rock shows alternating bands of the light- and
the dark-coloured components. All gradations are known
between a distinct granite and a highly laminated gneiss. For
the intermediate types the terms granitoid gneiss and gneissoid
granite are used. Gneiss may also be formed by the intense
metamorphism of beds of clay. This kind of gneiss is usually
more distinctly laminated and is liable to contain accessory
minerals such as garnet and sillimanite. The term paragneiss
is used to distinguish the rock of clay origin from that of
granite origin which is called orthogneiss.
Some authors use the word "gneiss" to designate any of
the plutonic igneous rocks which have acquired a laminated
structure through metamorphism; thus we have syenitic,
dioritic, pyroxenitic, and other gneisses,
c
34
ELEMENTARY GEOLOGY
SCHISTS. The schists are usually of finer lamination than
the gneisses, but if that term be used in the broader sense
it is difficult to establish a sharp line of division between the
two rocks. Schists may be defined as rocks of crystalline
structure, usually showing a pronounced lamination. They
may be formed by the metamorphism of either igneous or
sedimentary rocks. Schists are usually named from the most
conspicuous mineral present.
Mica schists are finely laminated rocks composed essentially
Photo, by J. Keele
FIG. 8. TYPICAL GNEISS, KILLALOE, HAGERTY TOWNSHIP, ONT.
of some variety of mica and quartz; thus we have biotite,
muscovite, sericite, and other mica schists. Mica schist passes
insensibly into gneiss by the gradual increase of feldspar.
Hornblende and chlorite schists result from the meta-
morphism of the basic igneous rocks in which pyroxene is
a prominent component. The alteration consists of the passage
of the pyroxene into hornblende or chlorite and the acquisition
of a banded structure. Some hornolende schists are fairly
massive and the laminated structure can be seen only on
MINERALS AND ROCKS 35
careful examination. Talc and epidote schists are other
examples of schists in which secondary minerals are present.
SLATE. Slate is a metamorphic rock resulting from the
strong alteration of shale. The familiar cleavage of slate is
not a parting parallel to the original bedding of the clay,
but is the result of terrestrial strains which have acted on the
rock and induced a parting at right angles to the direction of
pressure. Highly metamorphosed slate shows mica as a con-
stituent and is called mica slate', less altered types, without
a development of mica, are called clay slates.
OUARTZITE. This rock is metamorphosed sandstone: it is
usually very hard and compact, the grains of quartz being
closely pressed together and frequently cemented by secondary
silica into a remarkably hard rock. Naturally there are many
varieties of quartzite depending on the purity of the original
sandstone. Conglomerates and breccias give rise to corre-
sponding metamorphic rocks.
GREYWACKE. This is a very useful if somewhat indefinite
term ; it is applied to metamorphic rocks intermediate between
slates and quartzites. Greywacke results from the metamor-
phism of shaly sandstones: it is tough and usually breaks
with an irregular fracture on which ill-defined fragments of
the original rock, rather than distinct minerals, are to be
observed.
CRYSTALLINE LIMESTONE. Ordinary limestone under meta-
morphic influences acquires a crystalline structure and is then
termed crystalline limestone. The grain may vary from fine
to very coarse. Fine-grained types, when of sufficient beauty
for decorative purposes, are called marble, but this term is
of rather indefinite significance as it is used for limestones
other than crystalline if their appearance justifies their use
as decorative material. As in the case of unaltered limestones,
magnesian and dolomitic crystalline varieties are comrnon.
SERPENTINE. By the alteration en masse of basic igneous
rocks rich in the dark-coloured minerals, serpentine is formed
on a scale which justifies the use of the name for the rock
as well as for the mineral.
CHAPTER III
DYNAMIC GEOLOGY
THE earth is not an inert sphere endowed only with planetary
motions, but is constantly being moulded in all its parts by
the action of physical and chemical forces. The pull of gravity,
the effects of heat, light, and electricity, the power of chemical
affinity and other molecular attractions, and the results of
radioactivity all have their place in shaping and modifying
the earth as a whole and its various parts. Even living beings,
each individual insignificant, by cumulative effects may cause
important changes in the earth, so that biology as well as
physics and chemistry must be drawn upon to understand
the constant adjustments to which the earth is subject.
The sources of the energy at work in the world are to be
sought partly in the earth's internal stores of heat and partly
in energy radiated from without, principally from the sun.
It is evident that the work of the earth's internal heat will
be mainly subterranean and out of reach as far as direct
observation is concerned; while the heat, light, and other
energies coming from the sun play all about us and cause
most of the familiar phenomena by which the surface is shaped.
With the exception of tidal effects due to the pull of the moon,
and the relatively faint radiations reaching the earth from the
stars, the changes taking place are due either to the earth's
internal heat, giving rise to hypogene action, or to radiations
from the sun, the epigene forces. We may then divide Dynamic
Geology into two parts, Hypogene and Epigene: the first
dealing mainly with deep-seated forces, and the second mainly
with superficial ones.
HYPOGENE FORCES
It may be said generally that the earth is a heat engine.
Its interior is hot and heat is constantly radiating into space,
and as a result work is being done in various ways. It will
36
DYNAMIC GEOLOGY 37
be desirable to consider first the heat relations of the earth
and then the ways in which the work is done. In this con-
nection slow changes of level in the earth's crust are of great
importance. These may result in sudden adjustments of the
strata, causing dislocations, Assuring, and earthquakes, and
may permit molten rock to move below the surface, or break
forth on the surface, forming volcanoes. Slow transformations
of the minerals in rocks beneath the surface may take place
by means of pressure, motion, heat, and circulating liquids
connected with molten rocks, causing metamorphism. The
hypogene activities may be discussed then under the heads of :
Condition of the Earth's Interior.
Secular Changes of Level.
Earthquakes.
Volcanoes.
Metamorphism.
CONDITION OF THE EARTH'S INTERIOR
The surface of the earth consists of cold and solid rock,
where it is visible on the land, and the same is no doubt true
beneath the ocean, which at great depths, even within the
tropics, has a temperature not far from the freezing point.
In all parts of the world where mines or deep wells have been
sunk we find, however, that the temperature rises below the
depth of 50 or 60 feet at which seasonal changes cease. The
rate of increase varies a good deal, sometimes being as rapid
as i° F. in 28 feet (Comstock Lode), and sometimes as
slow as i° F. in 120 or 130 feet, as at the Calumet and
Hecla mine in Michigan. It is generally stated that the
average rate of increase in temperature is about i° F. in
60 feet, or i° C. in 30 metres or 100 feet. The most recent
and careful work, carried out in the sinking of wells in Penn-
sylvania and West Virginia, where a depth of over 7000 feet
was reached, gives an increase of i° F. in from 46 to 51 feet;
a much more rapid rate than has usually been found. The
deepest well, that of Clarksburg in West Virginia, reached
7386 feet, with an average rise of temperature of i° F. in
51 feet.
If one assumes the rate to be i° C. in 100 feet, as a round
38 ELEMENTARY GEOLOGY
number, and also that the rate continues the same for great
depths, it is evident that the temperature two miles below
the surface would be greater than 100° C., i.e. above the
boiling point; that at 20 miles it would be over 1000° C., far
above red heat; and that at a sufficient depth a temperature
would be encountered capable of melting any known substance
under ordinary surface conditions.
Levels at which equal temperatures occur may be called
isogeotherms.
It was believed in earlier times that the interior of the
earth, beneath the solid crust, was molten, or even, as some
thought, gaseous; but there are conclusive proofs that the
earth as a whole is solid, in fact even as rigid as steel. For
instance, earthquake waves are transmitted through the earth
at a speed possible only in a highly rigid solid; and the tides
of the ocean would be imperceptible if the earth were liquid
within a moderately thick crust, since the internal tides would
leave very little margin for oceanic tides.
We must assume then that no large part of the earth's
interior is liquid and either that the downward increase in
temperature gradually diminishes and finally ceases, or that
the pressure of the vast load of overlying rock compresses
the materials beneath, preventing the expansion necessary to
change a solid to a liquid. Perhaps both assumptions are
true. It should be remembered that our explorations into
the earth's crust have not gone beyond 7386 feet, less than
a mile and a half, while the earth's radius is nearly 4000
miles; so that we really know very little directly as to
conditions at great depths.
Unless one accepts the nebular hypothesis, which assumes
that the earth began intensely hot and has not yet lost all
its heat, the cause of the high temperature of the earth's
interior becomes a matter of interest, and several suggestions
have been made to account for it. The final result of most
kinds of work is to cause heat, so that mechanical work alone
on a sufficient scale could provide the necessary temperature.
This work might be due to compression, to tidal kneading
caused by the pull of the moon and sun, etc. Even chemical
action, such as the burning of fuel, has been suggested, though
this cannot be of importance. The most surprising cause of
DYNAMIC GEOLOGY 39
the heat below the surface of the earth has been made known
rather recently, in the discovery that the rocks making up
the earth's crust often contain radioactive substances which
are constantly giving off heat. Some physicists even state
that the heat provided in this way more than balances the
losses into space, so that the earth is really warming up and
not cooling down.
SECULAR CHANGES OF LEVEL
Except in earthquake regions one is apt to think • of the
earth's crust as immovable, to regard it as terra firma, and yet,
given a sufficient change of conditions and length of time,
very important changes of level may take place, amounting
even to many thousands of feet. So far as known, these changes
go on usually with extreme slowness, hence the term "secular"
changes of level. It is probable that most parts of the earth's
surface have changed their level within recent geological time,
and that some parts are now rising or sinking.
It is evident that to recognise these slow changes one
should have a standard of comparison, and the one adopted
is the mean level of the sea, reversing the usual impression
of the instability of the sea and the firmness of the land. As
the sea covers nearly three-fourths of the earth, and the
different oceans have broad connections, it will theoretically
take the shape of a spheroid of rotation under the combined
influences of the pull of gravity towards the earth's centre
and of the centrifugal force due to its rotation every twenty-
four hours. Unless there are changes in the amount of
water on the earth this spheroid should make a very constant
datum plane.
In reality, however, there are disturbing factors. Coastal
mountain ranges, like the Cordillera along the Pacific, un-
doubtedly pull the water towards them; and in great ice
ages vast volumes of water, perhaps millions of cubic miles,
are removed temporarily from the sea, lowering its surface
over the whole earth. The piling up of such a weight of ice
in the northern hemisphere must have shifted the earth's
centre of gravity to the northwards, which would mean a
raising of the level in northern seas and a sinking in the
40 ELEMENTARY GEOLOGY
southern hemisphere. It is probable that such changes in
the level of the sea at a given place may have reached one
hundred or even two hundred feet. It has been suggested
also that the total amount of liquid water in the world may
be steadily diminished in the process of weathering when
hydrous compounds take the place of anhydrous ones. On
the other hand, the steam given off by volcanoes represents
the transfer of water (magmatic or juvenile) from the earth's
interior to its surface. Perhaps the two processes roughly
balance one another. However, in a general way we may
consider the sea as forming a fairly constant base level with
\vhich to compare the land. Fortunately the sea leaves a
distinct mark in the form of beaches and wave-cut ter-
races with cliffs behind them where it has worked for any
length of time, so that its former levels can often be recog-
nised at a glance.
EVIDENCES OF SLOW CHANGES OF LEVEL IN RECENT
TIMES
Proofs of sudden changes of level connected with earth-
quakes are not uncommon, as will be mentioned later, but
historic evidence of gradual
changes is harder to get, pro-
bably because of the slowness of
the motion. One instance, that
of the supposed temple of Jupiter
Serapis near Naples, is usually
cited. This temple is reported
to have been repaired in Roman
times, when it must have been
on dry land. At present the
ruins of the temple are just
awash with the sea. Three
marble pillars which still re-
main standing show holes bored
FIG. Q. THE THREE STANDING in the marble by marine shellfish
"P to a level of about twenty
feet. It is evident that the
temple must have been sunk beneath the Mediterranean to that
depth and then raised to its present level ; and these changes
DYNAMIC GEOLOGY 41
took place in less than 1700 years. However, Naples is in a
volcanic region where rapid adjustments might be expected.
Proofs of such gradual changes within a few hundred years
have been found in Scandinavia, where the northern shores
of the Baltic in Sweden and the North Cape in Norway are
believed to have risen, while at the south end of Sweden, as
at Malmoe, paved streets beneath the level of the sea show
depression. Scandinavia seems to have been swinging on a
pivot, the northern end rising and the southern sinking, and
it is supposed that these movements are still progressing.
Some geologists believe that similar movements are taking
FIG. 10. RAISED BEACHES, SPITZBERGEN
place in America, but others oppose this, and it is probable
that the land here is nearly, if not altogether, at rest. There
are, however, unmistakable proofs that eastern Canada and
the north-eastern states have risen hundreds of feet in geologi-
cally recent times, since the ice of the Glacial period left the
region; for marine beaches, often still containing sea-shells,
are found in many places, gradually ascending northwards,
from 330 feet at Brockville to 600 feet on Mount Royal and
690 feet north-west of Ottawa. Similar beaches are found in
Labrador and around Hudson bay, as well as on the Pacific
coast, indicating that the whole region was depressed by the
load of ice and rose again when the ice was removed.
42 ELEMENTARY GEOLOGY
On the other hand, there is evidence of a sinking of the
land in some parts of eastern Canada, as near Wolfville in
Nova Scotia, where stumps of trees are to be seen at low tide,
fifty feet below the level at which trees grow at present, and
at Chignecto on the isthmus connecting Nova Scotia and New
Brunswick, where excavations for a proposed ship railway
disclosed a peat bed sixty feet below high tide.
Moderate changes of sea level, like those just mentioned,
may be accounted for naturally by a reference to the general
lowering of the sea, due to the amount of water required to
form the great ice sheets of the Glacial period.
This cause is, however, quite inadequate to account for the
old channel of the St. Lawrence, which can be followed to a
depth of 2000 feet or more at the edge of the continental
shelf, where the deep sea begins. It is evident that eastern
Canada stood at least 2000 feet higher than it does at present
when the river cut this ancient channel.
This great elevation came before the Ice age and was
followed by a depression when the raised beaches, men-
tioned earlier, were formed. Both stages belong to geologically
recent times.
CHANGES OF LEVEL IN MOUNTAIN BUILDING
Much greater changes of level are recorded in most moun-
tain ranges, as shown by the sea- shells enclosed as fossils in
the limestones and shales of the Rockies more than 10,000
feet above the sea. In the Andes such marine fossils are found
at 15,000 feet, and in the Himalayas at 20,000 feet or more.
The mountain tops have, then, been formed of sediments of
the sea bottom thrust up miles above their original position.
Almost all high mountains, as well as tablelands, give
evidence of their origin as marine sediments. The cause of
this will be discussed later.
DEPRESSION OF THE SEA BOTTOM
Evidence of profound depressions of the sea bottom are
naturally harder to find, since the proofs must be out of
reach beneath the ocean. Biologists and palaeontologists often
account for the distribution of plants and animals by assuming
DYNAMIC GEOLOGY 43
vanished continents, or at least land "bridges" connecting
continents or islands now separated by deep seas. One of
the most striking examples of this line of argument is founded
on the distribution of the wingless birds of the southern
hemisphere. The ostrich in Africa, the rhea in South America,
the apteryx of New Zealand, and the emu of Australia, as
well as the extinct aepyornis of Madagascar are all flightless
birds on southward projecting lands separated by seas 12,000
feet or more in depth. The supposition is that these lands
were once connected with one another, perhaps by way of
the Antarctic continent, and that the running birds then
made their way to their present homes. This evidence for
great depression of the land does not seem as certain, how-
ever, as that for great elevation in mountains, and there are
authorities who deny that continents and deep sea bottoms
have ever changed places.
ISOSTASY
There are proofs that at present the earth's crust nearly
approaches a condition of isostasy, i.e. that highlands are
high because they are made of lighter materials than lowlands,
and that the surface stands about at the level corresponding
to the specific gravity of the rocks beneath. If the theory
that the earth's crust is in a state of " isostatic equilibrium"
is correct, it makes an interchange of continents and ocean
depths very hard to account for, and suggests caution in
assuming great changes in the relations of land and sea.
EPEIROGENESIS AND OROGENESIS
Changes in level of the earth's crust may be divided broadly
into two kinds: epeirogenic (continent building), where con-
tinental surfaces are widely elevated or depressed without
much buckling or fracture; and orogenic (mountain building),
where bands of the lithosphere are thrust into folds or tilted
up as blocks that ride upon one another, forming ranges
of mountains.
The changes of level referred to in eastern Canada are of
the epeirogenic kind, while the Rockies and other western
mountain ranges afford excellent examples of orogenesis.
44 ELEMENTARY GEOLOGY
Orogenesis gives rise to the most striking relief features of
the land, and the building of mountain ranges results from
the concentration of tremendous thrusts along a line of
weakness in the earth's crust.
A region that has undergone orogenesis may have its
mountains carved down during the lapse of ages to low hills,
so that its mountainous character is lost, and subsequently
may be elevated or depressed in epeirogenic ways. North-
eastern Canada illustrates this excellently.
The terms used above apply to movements of the land;
but there can be no doubt that the crust of the earth beneath
the sea undergoes similar changes of level. Bordering moun-
tainous coasts there are often narrow, deep depressions,
"troughs" or "deeps," like reversed mountain ranges; and
there is good evidence of risings and sinkings of the sea
bottom on a broader scale.
DIASTROPHISM
Changes of level affecting the boundaries of land and sea
are known to have taken place at many times in the past;
but usually they have been of a local kind, the lowlands
settling to allow the advance of a shallow sea, or the sea
bottom becoming a coastal plain through a gentle rise of the
land. Recent developments of Stratigraphical Geology suggest,
however, that from time to time there have been widespread
changes of level, perhaps affecting all the continents at about
the same time, serving to mark off the major divisions of
geological time. Much importance is now attached to these
epochs of rising and broadening continents, and to the reverse
stages when shallow seas encroach widely upon the continents.
These readjustments of the earth's crust are included under
the term diastrophism, and there is some reason to believe
that such world- wide changes occur with a gigantic rhythm,
extending over millions of years, and that the climates of
the earth are modified to correspond with the broadening or
the narrowing of the land surfaces.
CAUSES OF CHANGES OF LEVEL
Assuming that the principle of isostasy is correct, changes
of level may be accounted for by changes of load. If a mile
DYNAMIC GEOLOGY 45
of ice is piled on north-eastern America, the region will sink
under the burden and the sea will encroach correspondingly
on the margin free from ice. If the ice melts, the load is
removed and the land rises. The raised beaches of Ontario
and Quebec may be accounted for in this way.
Where erosion is going on, the burden of the land will be
lightened and the land will rise ; while the shallow sea bottom
on which rivers are depositing sediments will tend to sink. In
this way thousands of feet of mud and sand may be laid down
at about the level of the sea, as happened at the Joggins, in
Nova Scotia, where 13,000 feet of sediments accompany the
coal measures, probably all formed at much the same level.
In the building of mountain chains a much more impor-
tant factor seems to come in, that of lateral thrust due to a
shrinkage of the earth as a whole.
If we imagine the earth's crust to be solidly adjusted for
a particular radius and the interior of the earth to be shrinking,
it is evident that the crust must yield to correspond. The
yielding will naturally take place along lines or belts of weak-
ness, where the rocks will be thrust into folds or broken into
long slices which ride upon one another, thus taking up the
slack due to the shrinkage. For instance, it has been estimated
that the eastern half of the Rockies at Bow Pass has been
narrowed twenty-five miles by the overriding of longitudinal
blocks, the outermost having been pushed seven miles out
upon the prairies.
This buckling and telescoping of the rocks is found in all
great mountain ranges, and is prepared for in a very singular
way. For ages before the range is elevated, sediments are
heaped on a slowly sinking band of shallow sea bottom until
20,000 or even 50,000 feet have accumulated in what may be
called a " geosyncline. " The firm floor beneath is depressed
into wanner levels and thus weakened, and finally the lateral
thrust overcomes its resistance and the mountains are raised
relatively suddenly. An illustration will be given later when
the history of the Rocky Mountains is taken up.
While this bending and breaking of the beds in belts of
weakness thousands of miles long is certain, and is attributed
usually to thrust of the sea bottom against a resisting mass
of land — a continent — there are difficulties in providing for a
46 ELEMENTARY GEOLOGY
sufficient amount of shrinkage to account for the requisite
shortening of the earth's circumference. The earliest sug-
gestion was that the earth had cooled and therefore contracted,
producing the lateral pressure ; but the amount of slack taken
up in the crumplings of the world's mountain chains far
exceeds any probable shrinkage due to loss of heat, and, as
mentioned earlier, it is doubtful if the earth really has been
cooling down.
Other suggestions have been the loss of lava, which comes
from miles beneath and is poured out on the surface, and the
loss of volatile constituents once contained in the earth's
interior, such as the steam and gases coming from volcanoes.
Compression of the materials of the earth under gravity and
also the rearrangement of the materials into new and denser
compounds are possible. If the earth was built up of planet-
esimals, small cold particles falling in from space, they may
have been loosely packed in the beginning and may have
been more and more closely crowded as time went on.
It must be admitted that no very satisfactory theory has
yet been proposed to account for the tremendous compression
of the earth's crust shown in mountain ranges.
MOVEMENTS IN THE ASTHENOSPHERE
Where a great area of land is elevated in epeirogenic changes
one must assume either that the supports beneath have ex-
panded, e.g. by rise of temperature, or that there has been
a movement of matter beneath to support the lithosphere in
its new position. The earth's crust is far too weak to stand
like an arch with a void beneath. The lithosphere rests upon
an asthenosphere, a sub-structure that is not liquid, that for
momentary stresses, such as earthquake waves, acts as a very
rigid solid, but that is loaded beyond its crushing strength
by the column of rock above. This asthenosphere is believed
to undergo slow motions, suggesting the flow of a very viscid
material, following up and supporting the rising crust above.
Where depression occurs, on the other hand, there must be
a slow outflow to permit the sinking of the lithosphere. These
extremely sluggish subterranean movements must exert a
dragging effect on the lithosphere above, and it has actually
DYNAMIC GEOLOGY 47
been proved by triangulation in the Californian earthquake
region that such movements have taken place, points on one
side of a great line of fracture having shifted their rela-
tive positions three or four metres since the region was
first mapped.
Given sufficient time, effects of great magnitude may be
produced by the gradual shiftings of the asthenosphere
beneath the solid crust.
EARTHQUAKES
It has been shown that great changes of level take place
at many points on the earth's surface, and that the rocks in
mountain chains are thrown into long flexures or even broken
FIG. II. SEISMOGRAM OF SAN FRANCISCO EARTHQUAKE, APRIL 1 8, IQO6
Recorded at the Observatory, Toronto, Ont.
asunder. Some of these movements appear to take place
quietly with no rupture of the beds, but others cause strains
which are suddenly relieved, the rocks breaking and re-
arranging themselves by faulting. Such sudden and violent
readjustments cause earthquakes. Naturally earthquakes are
most frequent and violent where mountains are being raised,
and especially where lofty mountain ranges rise rapidly beside
deep seas.
Of late years our knowledge of earthquake motions has been
put on a solid footing by the records of seismographs, instru-
ments for recording shocks. A simple form of seismograph
consists of a boom of steel wire lightly supported by a silk
thread and playing loosely in a socket. At the end of the
wire a small mirror reflects a ray of light down upon a band
of sensitised paper kept in regular motion by clockwork. The
ray of light is photographed as a straight line when the
48 ELEMENTARY GEOLOGY
seismograph is at rest, but when shaken by earthquake waves
the line becomes a zigzag or even swings quite off the band
of paper if the motion is violent. These instruments are so
sensitive that a heavy shock is recorded at stations thousands
of miles away. Seismographs at Toronto, Ottawa, and Vic-
toria have recorded earthquakes which took place in Japan,
San Francisco, Valparaiso, Jamaica, etc.
Three kinds of wave motions have been proved by the aid
of seismographs, one which travels on the surface of the earth
and two others transmitted through the earth along paths
with a somewhat inward curve. The surface waves are
slowest, with a rate of 3-8 kilometres (about 2 miles) per
second. The others have rates of 12 '8 kilometres (8*48 miles)
and 6-84 kilometres (4-53 miles) per second when at a distance
of 100° of arc from the starting point of the shock.
Though all great earthquakes are recorded by Canadian
seismographs no destructive earthquake has taken place in
Canada within historic times, since the Dominion is one of
the most ancient and stable parts of the earth. The most
serious Canadian earthquake on record occurred in Quebec in
1663, when for months there were small shocks swaying the
trees, so that the Indians said "the trees were drunk." The
only important effects noted were landslides along the river
banks. To study destructive earthquake action at first
hand a Canadian must go to other lands, though somewhat
severe shocks sometimes occur at Victoria and other points
in British Columbia.
The place of origin of an earthquake is called the epicentre,
an ill-chosen word, since the shocks do not begin at a point,
but along a plane which may even be hundreds of miles
in length. Since the breaking of the rocks which causes the
shock must take place within the "zone of fracture," the
centre from which the motions originate cannot be at any
great depth; and frequently the movement is evident at the
surface, one side slipping down a few feet, as in the Mino-
Owari earthquake in Japan (eighteen to twenty feet), and
the Shillong earthquake in India and Assam, when a shift-
ing of twenty-five or more feet caused a waterfall on
Chadrang river.
In the San Francisco earthquake (1906) the San Andreas
DYNAMIC GEOLOGY 49
fault was affected for a length of 435 kilometres, but the
displacement was mainly horizontal, amounting to four metres.
The displacement of the strata causing the earthquake may
take place with no perceptible warning and may be complete
in a few minutes; or it may continue from time to time for
months, as in the great Calabrian earthquake. The same
fault line may give rise to repeated earthquakes separated
by many years of quiescence, as in California. The greatest
vertical movement known is forty-seven feet, as shown by
the raising of a beach to that height in the Alaskan earth-
quake of 1899.
ACCOMPANIMENTS OF EARTHQUAKES. While the essential
feature of an earthquake is the dislocation and adjustment
of the solid rocks, there are other important features which
should be mentioned. The greatest destruction does not
usually happen on the solid rocks themselves but on overlying
drift deposits, and especially on "made ground." This was
well shown in the San Francisco earthquake, when the lower
part of the city on made ground along the harbour suffered
most, the effect being compared to the shaking of jelly in a
bowl. Great fissures opened in loose ground and much slump-
ing occurred, so that water pipes were crushed and railway
lines bent into sharp curves. Often the underground circula-
tion of water is affected, springs ceasing to flow or breaking
out in new places, and quicksand being forced up forming
miniature craters.
The most important secondary effect along sea coasts is
the huge wave which often follows up a withdrawal of the
sea, rushing far inland, destroying ships and buildings. During
the earthquake which destroyed Port Royal in Jamaica (1692),
the frigate Swan was driven over the tops of buildings and
thrown upon a roof which it broke.
From the human point of view a great earthquake is the
most terrifying of natural disasters, since a city may be
destroyed in a few minutes, and without warning tens of
thousands of people may be killed. There are few years in
which some catastrophe of the kind is not reported, such as
the earthquake which destroyed Messina with 75,000 of its
inhabitants in 1908, or the more recent destruction of the
city of Guatemala with great loss of life.
50 ELEMENTARY GEOLOGY
It has been found that certain types of structure resist
earthquakes best, those which are made of strong and elastic
materials, such as steel, being far more secure than, buildings
of brick or stone without reinforcement. The business portion
of San Francisco has been rebuilt largely with steel-framed
structures on this account.
DISTRIBUTION OF EARTHQUAKES. The causes of earthquakes
are bound up with the changes of level of parts of the earth's
crust, especially where young mountains rise near deep seas,
and accordingly we find that earthquakes are prevalent in
such regions, as around the shores of the Pacific, in the
Himalayan region, the East and West Indies, and the Medi-
terranean. Not all earthquakes have their origin on the land.
There have been settlings of blocks of the sea bottom along the
west coast of South America and between Calabria and Sicily
which have caused destructive earthquakes. Telegraph cables
have frequently been broken in the submarine disturbances.
VOLCANOES
The movements of molten rock at great depths are prob-
ably closely bound up with the folding and faulting connected
with mountain building, and hence with the causes of earth-
quakes, which are symptoms of such adjustments. Many of
these molten masses cease their movement long before reaching
the surface, so that their characteristics can only be studied
ages afterwards when erosion has removed thousands of feet
of overlying rock. Probably great masses of molten material
are set in motion and do important work beneath the axes
of rising mountain chains; but these masses become visible
to us only millions of years later, as in the Coast Range of
British Columbia or the Laurentian region of eastern Canada,
and it is proposed to defer a description of them until the
structural features of eruptive rocks are taken up, since our
knowledge of them is post mortem. Their actual operation we
cannot observe.
However, in many cases molten material conies to the
surface, causing one of the most dramatic displays of terres-
trial activity in the form of volcanoes. These are full of
interest and can be studied in many places. In early geological
DYNAMIC GEOLOGY 51
times there was great volcanic activity in several parts of
Canada, and in the west it is known that two or more vol-
canoes have been in eruption since the Glacial period, but
none has been reported as active within the memory of man.
The nearest active volcanoes to Canadian territory are
those of Alaska, but these have not been very carefully
studied, and other examples will be chosen to illustrate the
work of volcanoes.
The old idea that a volcano is "a burning mountain" is
of course incorrect. There is little actual combustion con-
nected with volcanoes, except as a bye-product of their work
when certain gases are given off and burn in the air. The
essential feature of a volcano is an opening or vent through
which molten rock may reach the surface. At the surface
the materials given off usually build a conical hill or mountain
with an opening on top, the crater (Greek word for cup).
The lavas of volcanoes in almost all cases are charged with
various gases, which seem to have been original constituents
of the magma, since in the quartz of granites, which cooled
at great depths below the surface, innumerable small in-
clusions of water or carbon dioxide can often be found under
the microscope.
Volcanoes give off, then, liquid rock, called lava, and gases,
including in the latter term all substances volatile at a high
temperature.
LAVA. The word lava does not mean a definite kind of rock,
but includes several species of eruptives ranging on the acid
side from rhyolite with seventy-five per cent, or more of silica
to basic rocks such as basalts which may contain fifty per
cent, or less of silica. Trachytes, andesites, etc., lie between
these limits. The properties of different lavas vary widely,
the more basic ones melting at a temperature of 1100° C. to
a very fluid magma, while the acid lavas have a higher
melting point and unless very hot are much less fluid. As a
result the basic lavas lose their gases more readily than the
acid ones and have comparatively quiet, unexplosive erup-
tions with thin, widely spreading lava sheets. Volcanoes with
acid lavas, on the contrary, have explosive eruptions, some-
times with no flow of lava, the whole mass bursting into small
fragments or even fine dust. Most volcanoes, however, are of
52 ELEMENTARY GEOLOGY
an intermediate kind with both lava flows and explosions,
thus building up a composite cone.
VOLCANIC GASES. These include water, hydrogen, hydrogen
chloride, chlorine, nitrogen, carbon dioxide, carbon monoxide,
sulphur dioxide, hydrogen sulphide, and sulphur, with smaller
amounts of other gases. The greater part of what is commonly
called the smoke of a volcano consists of condensing steam
coming either directly from the lava or from the burning of
hydrogen. Some authorities believe, however, that most of
the steam is really due to the evaporation of rainfall; and
ammonium chloride is thought by some to be an important
part of the volatile matter. It condenses as a white coating
FIG. 12. CRATER OF MOUNT KILAUEA, HAWAII
From Report of U.S. Geological Survey.
on the upper cone of Etna. The sulphur which is volatilised
or formed by combining one part of sulphur dioxide with two
parts of hydrogen sulphide is deposited in craters approaching
extinction.
VOLCANOES WITH VERY FLUID LAVAS. Two Hawaiian vol-
canoes, Kilauea and Mauna Loa, are famous for their very
fluid basaltic lavas, giving rise to non- explosive eruptions.
Kilauea (4000 feet) has been observed for many years and its
habits are well known, and Mauna Loa, twenty miles away
and nearly 10,000 feet higher, has similar eruptions. Owing
to the fluidity of the lava of which these mountains have
been built their slopes are very gentle, about seven degrees,
and the top has almost the appearance of a plain, with a large
steep-walled and flat-bottomed depression, the crater, in which
there is usually a small lake of liquid lava, giving off gases
DYNAMIC GEOLOGY 53
freely in little spurts from its surface. For years the lava
may slowly rise in the crater, till at length the pressure of
the lengthening column causes it to burst a way out some-
where on the flanks of the mountain and flow as a bright
stream, spreading widely till it cools. Meantime the level of
the lava pool in the crater sinks hundreds of feet. All goes
on quietly as a magnificent spectacle, sometimes including a
brilliant fountain springing hundreds of feet into the air. The
rapidly flowing stream in one case poured over a cliff into the
sea as a fiery fall a mile wide. The longest stream recorded
came from Mauna Loa and reached a length of sixty miles
before cooling and congealing.
Flows of a similar kind occasionally come from long fissures,
as at Laki in Iceland, where for a length of twelve miles lava
welled out, making a wide level floor and completely occupying
a river valley.
It is probable that some of the old basaltic lava plains,
covering 200,000 square miles of western Canada and the
Columbia region to the south, where few or no cones or craters
can be found, were formed in the same way; and the Deccan
traps of central India and also the great lava plains of southern
Brazil and Uruguay, covering many thousand square miles,
are additional illustrations.
VOLCANOES WITH EXPLOSIVE ERUPTIONS. At the other end
of the scale there are very viscid rhyolitic lavas charged with
gases which cannot escape easily and quietly, but at last,
as they reach the surface where the pressure is diminished,
explode violently and fling red-hot materials in all directions.
A well-known example of this type of eruption was that of
Krakatoa in 1883. This small island in Sunda Straits near
Java burst into a terrifying eruption which scattered bombs
for twelve miles around, hurled fragments as large as one's
fist twenty-five miles, and overwhelmed all the adjoining
coasts and plantations with ashes and dust. The finer par-
ticles of dust reached the upper air currents and were carried
round the world, causing remarkable red sunsets which .aroused
interest everywhere.
Much of the material flung off consisted of pumice, a variety
of lava so filled with air vesicles as to float, and Sunda Straits
were for a time blocked with the floating masses, which
FIG. 13. MONT PELEE
DYNAMIC GEOLOGY 55
gradually drifted away or were waterlogged and sank. Large
pebbles of this pumice thrown up by the waves can still be
found on the north shore of Australia, 2000 miles away, and
the sea bottom over hundreds of thousands of square miles
must be strewn with them. This violent explosion caused a
sea wave which did much damage on neighbouring coasts
and reached West Australia, 1800 miles distant. In many
ways the effects were like those of an earthquake of the usual
kind. In a few days the eruption was over and it was found
that about a third of the island had been torn to pieces and
had disappeared. The amount of rock ejected has been
estimated at eighteen cubic kilometres.
The eruption of Mont Pelee on the French island of
Martinique in 1902 was of the same type. The steam and
gases from the explosions, charged with hot particles, flowed
down the mountain-side and in fifteen minutes destroyed the
city of St. Pierre with 30,000 people.
No fluid lava came to the surface in this eruption, but
after the great explosion a curious obelisk or spine of plastic
but very porous lava was pushed up from the crater, at one
time reaching 1800 feet in height. It was not a permanent
feature but soon crumbled to debris.
Accounts of the recent eruption of Katmai in Alaska put
it in the same class with the eruptions mentioned above.
INTERMEDIATE TYPES OF VOLCANOES. Most volcanoes are
of an intermediate type and are built up partly of lava streams
and partly of loose materials due to explosion. The best-
known and longest-studied volcano in the world, Mount
Vesuvius near Naples, may be taken as an example.
Its predecessor, Mount Somma, was thought to be an
extinct volcano with a large crater, the whole overgrown
with trees or bushes; but in 79 A.D. an explosive eruption
took place, destroying with its showers of ashes and red-hot
stones two cities near its base, Pompeii and Herculaneum, as
recorded by the younger Pliny. On the ruins of Somma
Vesuvius was built, and from time to time since then it has
been in eruption, lava streams pouring out in various direc-
tions and the surrounding towns and vineyards suffering
from the fall of ashes and bombs. The size and shape of the
crater and the height of the summit have undergone many
56 ELEMENTARY GEOLOGY
changes, and occasionally an inner cone has been built up
within the main crater.
The lava given off is not very fluid, moves sluggishly and
with constant breaking and rolling over of the hardening
black crust formed by cooling. Occasionally this crust grows
so strong that the liquid lava within flows on and leaves the
shell as a long irregular tunnel. When in moderate eruption
great bubbles of lava seem to be raised within the crater till
the tension of the steam beneath becomes too great and the
bubble bursts, flinging red-hot fragments in all directions.
Photo, by E. S. Moore
FIG. 14. ERUPTION OF NGAURUHOE, NEW ZEALAND, IN 1914
This may go on with much regularity, an explosion about
every half-minute. Meantime a tall column of steam rises
some thousands of feet and drifts to one side with an upper
air current, the form resembling that of an Italian stone pine.
At night these explosions and the yellow streams of lava make
a brilliant display, and may be seen for sixty miles away on
the Mediterranean.
Etna, with its two hundred parasitic cones, has a still longer
history, reaching back for more than 2000 years.
CALDERAS. Since the materials for the eruptions come
from beneath, there is a tendency for volcanoes to collapse
after cubic miles of molten rock have been removed from
DYNAMIC GEOLOGY 57
under their foundations by successive eruptions. The whole
central part of the mountain may thus sink out of sight,
leaving a vast round depression with steep cliffs as walls.
Such an arrangement is called a caldera (caldron), and in
many cases the hollow is occupied by a lake. In other
cases it may be somewhat flatly floored, and if the volcano
has not become extinct there may be one or more active
cones and craters within it.
Crater Lake in southern Oregon, six miles long and four
miles wide, enclosed by cliffs 500 to 2000 feet high, is the
FIG. 15. CRATERS AND CINDER CONES, MOUNT ETNA
Eruption of 1892.
best example in North America. A small later cone forms
an island in it. Larger examples are found in Italy, such as
the beautiful lake of Albano, and the Lago di Bolsena which
has diameters of eight and a half and seven and a half miles.
One of the largest known is the caldera of Aso in Japan,
which is fourteen miles by ten in dimensions and has an
active volcano rising from its floor.
SUBMARINE VOLCANOES. Volcanoes are not confined to the
land, but may build up mountains from the sea bottom in
regions of disturbance. Some of them are known to us only
from their conical shape as shown by soundings; but there
are numerous examples where the volcano has risen above
sea level, forming an island. Graham's island, which appeared
58 ELEMENTARY GEOLOGY
in the Mediterranean near Sicily in 1831, was formed of loose
materials and was later washed away, leaving only a shoal.
In 1793 a new island rose with great commotion in Alaskan
waters, and two others have risen in later years, forming the
Bogoslov islands.
The greatest instance of the kind is found in the Hawaiian
islands, built up from profound depths in the Pacific almost
entirely of volcanic materials. If they stood upon dry land
some of their summits, like Mauna Loa, would be the highest
mountains in the world. This work was done long before
historic times, however.
DISTRIBUTION OF VOLCANOES. Volcanoes, as one might
expect, are usually found in earthquake regions, so that a
map of the one would roughly give the distribution of the
other. A great irregular circle of volcanoes, active or ex-
tinct, surrounds the Pacific. On the western side they are
numerous in Alaska, the Pacific States, Mexico, Central
America, and the Andes of South America. Mount Erebus
in Antarctica and the New Zealand volcanoes to the south
are followed by volcanic islands in the Philippines and Japan
on the east, while volcanoes in Kamtchatka and the Kurile
and Aleutian Islands finish the girdle of fire about the greatest
ocean. Beside this there are volcanoes scattered over the
Pacific, some, like those of Hawaii, built up from great depths.
A more scattered row of volcanic islands, beginning with
Jan Mayen and Iceland in the north, and including the Azores
and Cape Verde islands, runs down the centre of the Atlantic;
volcanoes occur also in the Mediterranean, and are very
numerous in the East Indian islands; while in the western
hemisphere a curved row of volcanic islands occurs in the
West Indies.
This distribution along lines of adjustment where moun-
tains are rising or blocks of the sea bottom are sinking is
natural, since here only can we imagine the formation of
channels by which molten rock can reach the surface.
CAUSES OF VOLCANOES. The actual source of the lava is, of
course, out of reach in the depths; but from what is known
of the rate of increase in temperature with depth one can
assume that some miles below the surface the heat would be
sufficient to melt ordinary rocks under surface conditions.
DYNAMIC GEOLOGY 59
One would expect that at a given depth there would be a
continuous sheet of molten lava waiting to escape through
any opening to the surface. For reasons given earlier, we
know that the earth as a whole is extremely . rigid, so that
no continuous sheet of molten rock can exist a short distance
below the surface. In reality the lava supply of volcanoes
must come from relatively small local pools. Even close
neighbours, like Mauna Loa and Kilauea, only twenty miles
apart, must have distinct sources of supply, since the lava
of Mauna Loa rises about 10,000 feet higher than that
of Kilauea.
Various explanations have been given to account for these
local pools of lava. It has been suggested that at a given
depth, where the heat should be great enough to melt erup-
tive rocks, the immense pressure of overlying materials
prevents liquefaction, since a rock in melting must expand.
Basalt, for example, expands four per cent, when melted.
One might suppose that any relief from pressure, such as
the rise of a fold or the tilting of a block of the earth's crust
in mountain building, might relieve the layer from pressure
at a given point, and allow the potential lava to expand and
rise through any opening to form a volcano.
If this explanation is correct, one would expect volcanoes
to accompany all great mountain ranges, which is far from
being the case. One thousand miles of the main range of the
Canadian Rockies consist entirely of sedimentary rocks, and
the only eruptions in the range occur at its southern end,
where there are some beds of ash and a small area of nepheline
rock, but no recognisable volcano. Other areas of recent
mountain building show a similar lack of volcanoes, as in
the Alps and Himalayas. On the other hand, in some lofty
and recent mountain ranges volcanoes are frequent, the
Andes being a good illustration.
The mere opening up of a channel, together with relief from
pressure of overlying rock, does not account for any large
number of volcanoes; but the settling down of large blocks
or arcs of the crust is a very frequent cause. This may be
seen in the volcanoes along the great African rift, and is
probably illustrated by the festoons of volcanic islands on
the north and east of the Pacific, as well as in the curve of
6o ELEMENTARY GEOLOGY
volcanic islands in the West Indies. In these cases probably
the pressure of the sinking block has aided in forcing lava
up round the fractured edges.
Occasionally a volcano or a group of volcanoes rises through
what appear to be undisturbed sediments, and some geologists
believe that the molten magma can drill its way up without
any open fissure, by melting the rocks above or by "stoping"
the overlying blocks until the surface is reached.
In addition to the earth's original heat as assumed above,
there are other possible sources of heat of a more local nature.
The crushing of rocks in mountain building must generate a
large amount of heat, which has been suggested as a cause
of volcanoes. An unusual accumulation of radioactive
material, also, might supply heat enough to melt rocks
locally and so cause a volcanic eruption.
It must be admitted that the problems connected with the
melting of the lava and its ascent through miles of solid rock
to the surface remain quite obscure.
SOURCES OF THE GASES OF VOLCANOES. The gases of vol-
canoes, especially steam, seem almost as important in eruptions
as the lava itself, and many of the phenomena mentioned
above are due to the action of the volcanic gases. The source
of these volatile constituents of the lava has been much
debated and cannot be considered as finally settled.
Some geologists believe that the water given off in vast
quantities as steam in most volcanic eruptions is of surface
origin, rain or snow water or the water of lakes or the sea,
which has settled into the rocks and has been in a sense
dissolved by the molten magma. They point to the fact
that volcanoes are almost always found near the sea or as
islands rising from the sea bottom.
Not all volcanoes, however, are really near the sea or some
great lake which might supply water. Some of the finest and
loftiest volcanoes in the world, such as Chimborazo, Cotopaxi,
and Ollague, all reaching 20,000 feet, rise from the vast, dry
tableland of the Andes, 10,000 or 12,000 feet above sea level
and 150 miles or more from the coast. Ollague, in northern
Chile, stands in the driest desert in the world. In such cases
no surface supply is available, and the ascending lava must
have brought its abundant waters from the depths.
DYNAMIC GEOLOGY 61
Probably most geologists believe that the lavas are originally
charged with water or its constituent gases, and with the
compounds of sulphur, chlorine, carbon, etc., given off in
eruptions. These original gaseous substances dissolved in the
molten rock arc called "magmatic" or "juvenile." The
term magma is used for molten matter occurring in the
depths, while the same molten material is called lava when
it occurs in a volcano. The word juvenile, which is not so
commonly used as magmatic, implies the recent appearance
on the surface of these gases or fluids set free from the depths.
EXTINCTION OF VOLCANOES. Volcanoes may be active for
only a few days and then cease their work and become
extinct, like Monte Nuovo near Naples ; or they may continue
active for thousands of years, like Etna, whose history reaches
back to 600 B.C., as far as the records go.
Volcanoes may cease their work and become dormant for
years or centuries and then break out afresh, as Somma,
supposed to be extinct, became transformed into Vesuvius.
Ultimately the supply of lava diminishes and no longer
reaches the crater, the last remnant congealing in the channel
beneath and sealing the opening.
Active volcanoes have been estimated to number about five
hundred, but extinct volcanoes run into the thousands. The
only known volcanoes in Canada sufficiently well preserved
to display their typical form are extinct: one a small cinder
cone with a crater burst by a little lava stream, in the Yukon
territory; the other Mount Garibaldi, a fine peak with several
lava streams, forty miles north of Vancouver.
Though even extinct volcanoes are rare in Canada, typical
volcanic products are widely found in the older geological
formations. Lava streams and plains of Cenozoic age occupy
much of central British Columbia. A band of white volcanic
ash lies just beneath the soil for many miles along the Yu-
kon river. Very ancient lavas (Keewatin) occur in northern
Manitoba and in northern Ontario. In the latter province
they once covered many thousands of square miles.
Later lavas (Keweenawan) have a thickness of more than
20,000 feet near Lake Superior, and a thick sheet of tuff
(volcanic ash) of nearly the same age occurs near the Sudbury
nickel mines.
62 ELEMENTARY GEOLOGY
The stumps of old volcanoes (Devonian) make striking hills
near Montreal, and volcanic rocks of a much later age (Tri-
assic) form the cliffs of Blomidon in Nova Scotia.
Except for recent feeble activity of Lassen Peak in the far
west, the United States has only extinct volcanoes. A
majestic row of them, beginning with Mount Baker just
south of the British Columbian boundary, runs south into
California. For really active volcanoes in North America one
must visit Alaska or Mexico. Mount Orizaba, the highest
volcano (18,300 feet) in Mexico, is perhaps extinct, since its
top and crater are snow covered; but Mount Colima (12,000
feet) and many smaller volcanoes are still active.
FUMAROLES AND HOT SPRINGS
Long after the last eruption of a volcano, steam and certain
gases may pass off from the slowly cooling lava beneath the
surface. The steam may escape under pressure, forming a
fumarole, or, where the lava has cooled farther, only hot
water may be given off, forming springs which deposit sinter
(mainly silica), often forming beautiful basins.
Probably the most striking development of fumaroles in
the world is to be found in the Valley of Ten Thousand
Smokes, near the volcano Katmai in Alaska. As no smoke,
only vapour of water, is given off, the name seems badly
chosen. In this valley an area of some square miles is riddled
with openings from which steam escapes.
Hot springs are found in almost all volcanic regions, but
they are not confined to them, since waters sinking far enough
into the earth may become heated and rise to form springs.
A good illustration is to be found in the Banff hot springs
in the Rocky Mountains, which are fifty miles from the
nearest known eruptive rock.
GEYSERS
While fumaroles and hot springs are common in dying vol-
canic regions, "geysers," which intermittently spout columns
of hot water into the air, are known only in three places:
Iceland, where the name originated, New Zealand, and the
Yellowstone Park. Years ago a geyser near Rotorua in New
DYNAMIC GEOLOGY 63
Zealand flung its jet of hot water 1600 feet into the air, but
an eruption of the near-by volcano Tarawera interfered with
its subterranean channels and put an end to the display.
The Yellowstone Park geyser region is at present much
the most extensive and interesting in the world.
The cause of these recurring eruptions of hot water and
steam is to be found in the superheating of steam in the
lower channels that feed the geyser. The column of cold
water in the upper part of the vent presses upon the hot
water beneath, raising the boiling point until the temperature
is high enough to generate suddenly a great volume of steam
which flings the water above as a jet into the air.
The source of the water in hot springs and geysers is prob-
ably largely rain and melting snow; but part of the supply
may be magmatic in origin. Such hot waters sometimes
contain salts of the metals in solution and deposit metallic
minerals in the sinter forming their basins.
Probably similar hot waters circulating in fissures far below
the surface in the vicinity of masses of cooling eruptive rock
deposit ores and other minerals in veins, which may become
of importance to the miner in later ages. Most of the ore
deposits of the world were formed in this way.
METAMORPHISM
It has been shown that even molten rock contains water
or other volatile substances in important amounts, and this
is commonly true also of the sedimentary rocks, most of
which were formed beneath the sea. Water is the medium
through which most chemical reactions take place; hot water
is a better solvent than cold water; and pressure has been
proved to increase the activity of water. Where rocks, whether
eruptive or sedimentary, are exposed to the action of hot
water under pressure, changes may be expected; but mag-
matic waters coming from hot eruptive rocks, charged with
silica and other substances in solution, will be most effective
in this respect.
Rocks may be exposed to these conditions simply because
they are at great depths, or because eruptives have penetrated
to beds at higher levels. Frequently both depth and eruptive
64 ELEMENTARY GEOLOGY
magmas may be at work. The effect of heat, pressure, and
water containing various substances in solution in attacking
the minerals of rocks and transforming them into other
minerals is called metamorphism. This may imply only a
rearrangement of elements already present or the removal
of some elements with the introduction of others.
Sometimes a distinction is made between contact meta-
morphism, due to the presence of a cooling eruptive sheet or
mass near by, and regional metamorphism, where the changes
take place on a large scale and usually at a greater depth;
but there is no sharp boundary between the two processes.
Metamorphism is greatly helped by crushing and shearing in
connection with mountain building, since this gives easy
access for fluids, and where mechanical work of this kind is
important the term dynamic metamorphism is sometimes used.
EFFECTS OF METAMORPHISM ON SEDIMENTARY ROCKS. The
usual sedimentary rocks, shale, sandstone, and limestone, are
quite differently affected by metamorphism and should be
taken up separately.
Shale, which is merely consolidated clay, is changed into
slate by pressure and shearing with a small amount of re-
crystallisation. In the harder slates, like those used for
roofing, many small scales of mica or chlorite may be seen in
thin sections and much of the muddy material has been
changed into definite minerals. In contact metamorphism
certain compounds of silica and alumina are apt to form,
such as staurolite, a hydrous silicate of iron, alumina, and
magnesia, or andalusite or sillimanite or cyanite, silicates of
alumina. A more complete recrystallisation will give rise to
phyllite with a shimmering surface due to the formation of
sericite; and finally the whole of the materials may be re-
arranged into quartz and mica, forming mica schist, or into
quartz, feldspar, and mica, forming gneiss. Often garnets and
other crystalline minerals are formed at the same time.
Sandstones are differently acted on according to their com-
position, pure quartz sands being merely cemented by the
outgrowth of the quartz grains till the whole becomes a mass of
solid quartz, called quartzite. Argillaceous sands turn to mica
schist ; and arkoses, or sandstones with much feldspar, become
gneisses undistinguishable from some metamorphosed shales.
DYNAMIC GEOLOGY 65
Limestones and dolomites, if pure, are simply rearranged
into crystalline calcite or dolomite, forming marble. If impure
a great variety of minerals may result, including micas,
varieties of hornblende or augite, graphite, etc.
Coal loses its volatile matter, changing first to anthracite,
which except for ash is nearly pure carbon, and afterwards
to graphite.
The metamorphism of tuffs or ash rocks depends mainly
on the composition of the materials, and results in sericite
or mica schists or gneisses for the acid rocks, and in chlorite
or hornblende schists for the ordinary basic rocks. Massive
eruptives are less attacked, unless they have been crushed
and sheared, when results like those just mentioned will be
produced. Very basic rocks like peridotites are transformed
by hydration into serpentine or talc; but many authorities
would include this change in weathering rather than in
metamorphism.
EPIGENE FORCES
WEATHERING
The epigene forces, as noted earlier, are those which are
derived mainly from the sun and perform their work on
or near the surface of the earth. They are familiar to us,
since they are in operation all around, and on that account
pass almost unnoticed. Their ceaseless activities are con-
stantly moulding the land and giving it the contours of
plain and valley, hill and mountain, that meet our eyes
everywhere, but the work usually goes on so slowly as to
be quite overlooked.
Beginning with a world whose outer crust is of solid rock,
the first operation to be studied is naturally that of the
crumbling and decay of rocks, sometimes expressed as the
effects of the "tooth of time." The most important agents
in this work are water, the gases of the air or of the soil, and
changes of temperature, all commonplace and unimpressive
in their action, yet capable of destroying in time the most
resistant rocks.
Water is present everywhere as a variable constituent of the
E
66 ELEMENTARY GEOLOGY
air, and falls as rain or snow, changing from the gaseous to
the liquid or solid state; and pure water can dissolve salt
or gypsum, which are rarely found on that account except in
deserts. The oxygen of the air is a powerful chemical agent.
Carbon dioxide is found in small quantities in the air, about
4 parts in 10,000, and in larger amounts in soils where
organic matter is decaying. Heat expands and cold contracts,
tending to destroy the cohesion of rocks and to split off frag-
ments. The combined effect of these agents is weathering.
OXIDATION. Many eruptive rocks contain compounds not
completely oxidised, one of the commonest being ferrous
oxide, which forms part of most of the green minerals, such
as augite or hornblende. Oxygen in the presence of moisture
tends to combine with the ferrous oxide to form the more
oxidised compound ferric oxide, which is red, or if hydrated,
brown, so that the work of oxidation destroys the mineral
attacked and forms limonite. This type of weathering causes
rocks like basalt or diorite to change their colour from green
or black to brown, and so weakens them that they are softer
and more easily attacked by other forces. The change in
colour of blue clay, which weathers brown, illustrates the
same effect.
CARBON DIOXIDE. The most effective reagent in weathering
is carbonic acid, the combination of carbon dioxide with
water, which is only feebly acid, but slowly dissolves certain
minerals and decomposes others. One of the most important
sedimentary rocks is limestone, formed of calcite or carbonate
of lime, which is soluble in carbonic acid. All exposed lime-
stones and marbles are being dissolved and carried down to
the sea as a result of this action, and almost all spring and
well waters are charged with lime. The effects are well shown
in cemeteries, where marble monuments a few years old lose
their polish and begin to crumble, especially on the side
toward the rainy winds. In fifty years the inscription is
generally illegible. Dolomites are much more slowly attacked.
Among the eruptive and schistose rocks, certain feldspars
of great importance, such as orthoclase and the soda plagio-
clases, are attacked by carbonic acid which decomposes the
feldspar into a soluble silicate of potash or soda, and an
insoluble silicate of alumina, which is left behind in the
DYNAMIC GEOLOGY
67
hydrated form as kaolin or clay. Since the feldspars make
the bulk of most eruptive rocks and gneisses, this completely
disintegrates them, leaving a crumbling sand instead of a
solid resistant rock. Several other silicates are attacked in
a similar way.
This process is comparatively slow, and its results are not
yet very apparent in the glaciated regions of Canada and
the northern United States, but are well displayed in granite
FIG. 1 6.
HONEYCOMB WEATHERING IN STRATIFIED ROCKS, LAKE
TIMISKAMING, QUEBEC
regions never covered by the ice, for instance at Washington,
D.C., in Brazil, or in the Klondike.
CHANGE OF TEMPERATURE. The lighting of a fire on bare
rock often splits off thin slabs by the rapid expansion of the
part immediately beneath. The farmer sometimes uses fire
setting followed by a dash of cold water to break up boulders
in his fields ; and before the days of explosives this was the
best method of breaking down rock in mining. There is no
doubt that the ordinary changes of temperature have a similar
effect, though they act much more slowly. In desert regions,
where the dry atmosphere permits rapid radiation of heat at
night, the extreme temperatures of day and night may even
FIG. 17. TALUS FORMED BY ACTION OF FROST, NIPIGON RIVER. ONTARIO
DYNAMIC GEOLOGY
69
range from 150° F. to the"J freezing point, and slices and
fragments of rock are constantly being split off from exposed
rocks, which are gradually buried under the chips due to their
own decay.
In climates like ours, however, frost is the great quarryman,
heaping a pile of blocks called a talus at the foot of every
cliff. The fragments broken off expose fresh surfaces for the
work of weathering which greatly aids the process.
RAIN ACTION. In most parts of the world rain falls fre-
quently. Even in deserts violent rain sometimes falls, perhaps,
however, only after the lapse of years. In the nitrate region of
northern Chile it is said that the last rain fell sixty-five years
ago, yet the superficial effects of rain erosion may sometimes
be seen there.
A single drop of rain exerts a most insignificant force for
geological work, but the cumulative effects of the drops in a
storm may be important. About thirty inches of rain fall in
the year in Ontario, having a weight of 2,200,000 tons per
square mile. In sum, then, the force exerted by the falling
drops is very important. The gullying of hilly fields after a
heavy shower and the muddy waters of the overflowing
streams give evidence that a powerful force has been at work.
More striking illustrations are supplied by the
earth pillars frequently seen in mountain valleys.
These are carved by rain
from boulder clay. The clay
is readily removed where un-
protected, but where some
boulder occurs as a cap the
washing away of the sur-
rounding clay leaves a pillar,
There may be dozens
of such pillars, each
sheltering under its
stone. If the stone
is dislodged the pillar
becomes a cone and
soon wastes away.
Earth pillars are often twenty-five or thirty feet high, and
serve as monuments to rain action. In the long run cubic
FIG. 1 8. EARTH PILLARS
DUE TO RAIN EROSION OF
BOULDER CLAY, ROCKY
MOUNTAINS
70 ELEMENTARY GEOLOGY
miles of clay are removed by rain from the sides of valleys
like that of Bow river and swept down to the river itself.
Part of the rainfall runs off quickly to the nearest stream;
this is sometimes called the run-off; and part sinks into the
ground. On rock surfaces almost the whole of the rain flows
off directly. On sand or gravel almost the whole sinks in and
is lost to sight. The types of work performed by these two
divisions of the rainfall differ greatly, though ultimately,
perhaps after months or years of underground wandering,
the part that disappears into the soil usually reappears as
springs and joins the regular circulation of the streams.
GROUND WATER
The spaces between the particles of soil or of porous rocks
are very small, sometimes only capillary, and the water
FIG. 19. UNDERGROUND WATERS
Water from rain and melting snow sinks into the soil until arrested by some impermeable
bed, such as clay or shale. The level of ground water rises after a wet season and sinks
after a dry one, leaving shallow wells without a water supply. Springs occur along the
sides of slopes where the top of the impermeable layer is exposed.
soaking in can move only slowly; nevertheless as "ground
water" it is constantly urged downwards by gravity and
makes its way just above some impermeable layer toward the
lowest point, where it may emerge as a spring. The level of
ground water varies with the season, being highest as a rule
in spring, when the ground has been soaked with rain and
melting snow, and lowest after the droughts of summer. In
the country parts of Canada the water supply comes some-
times from springs but more often from wells, both dependent
on ground waters. A well, if not deep enough, may fail toward
the end of summer because of the sinking of the ground water,
and not all springs are perennial.
Since the ground waters in their slow motion underground
DYNAMIC GEOLOGY 71
generally dissolve lime by the aid of carbonic acid and also
obtain small amounts of gypsum (calcium sulphate) and of
salt (sodium chloride), well and spring waters are generally
"hard," that is, contain compounds of lime. This is noticed
in washing, when the fatty acids of the soap combine with
the lime, giving a "curdiness" to the water, and also in the
"furring" of the tea-kettle, where the boiling away of the
water and the driving off of carbon dioxide make a coating
of carbonate and sulphate of lime. The salts and gases dis-
solved in such waters give them a more pleasant flavour than
the purer but more insipid rainwater with which they began.
Not infrequently a little sulphate of iron has been picked
FIG. 2O. LANDSLIP, FRANK, ALBERTA
up also, giving a slight inky taste to which one presently
gets accustomed.
LANDSLIPS. The soaking of rain into the ground may so
far soften beds of clay or silt or fine sand that they can no
longer support the load above, and large slices or even square
miles of loose deposits may slip on such a lubricated layer
into the nearest valley. Such a movement is called a landslip
or landslide, and is illustrated along clay cliffs almost every
spring. Destructive landslides have occurred at several points
in the province of Quebec, as at St. Albans in 1890, when an
area of clay and sand 2 J miles long, i mile wide, and from
10 to 250 feet thick slid down into the valley of St. Anne
river, destroying farms and houses.
The most serious landslip recorded in Canada is that which
occurred at the coal-mining town of Frank in Alberta, on
July 4, 1903, when a large part of the top of Turtle Mountain
slid into the valley, running right across it and rising 400 feet
72 ELEMENTARY GEOLOGY
on the other side. It is estimated that 80,000,000 tons of lime-
stone were thus spread out for nearly two miles across the
valley, destroying part of the town and burying the Crows-
nest railway for some distance. It is probable that the work
of frost in fissures on the mountain top was mainly responsible
for this disaster.
Much more extensive landslips have taken place in the
Alps, as that of Rossberg which buried several villages,
and in the foothills of the Himalayas, where a landslip
dammed back a tributary of the Ganges, forming a large
temporary lake.
ARTESIAN WATERS. In some places surface waters find their
way into porous beds, generally of sand or sandstone, called
aquafers, between impermeable beds of clay or shale, and in
this way may travel long distances and reach great depths
where they may become warm or even hot. If some region
of faulting provides fissures by which they can reach the
surface, as at Banff, copious hot springs result. Where there
is no such natural outlet the drilling of a well may give escape
to the water, if there is sufficient slope to provide a "head,"
and there may be a permanent flow of artesian water. Such
supplies may be tapped in desert regions, hundreds of miles
from their source in some range of mountains which gathers
the rain clouds by reason of its elevation. Parts of Australia
and some of the Saharan regions have important supplies of
water drawn from artesian sources.
MINERAL SPRINGS. While all spring waters contain mineral
matters such as lime, gypsum, and salt in solution, the name
"mineral spring" is given only to those containing less usual
ingredients. They may be sulphur springs containing hydro-
gen sulphide, chalybeate springs strongly charged with iron
compounds, saline springs containing various salts in solution,
etc. Mineral springs are often of medicinal value, as at Banff,
Alberta, and at Caledonia, Preston, and St. Catharines in
Ontario. Some mineral springs, such as those of Saratoga,
New York, and of Carlsbad in Bohemia, have been explained
as consisting of magmatic or "juvenile" waters coming
from deep-seated eruptives, instead of surface waters which
have ascended after reaching a great depth.
CAVES. In limestone regions waters containing carbon
74 ELEMENTARY GEOLOGY
dioxide may follow joint fissures or other small openings and
slowly dissolve out underground channels, which may ulti-
mately be widened and deepened into great caverns sometimes
running for a number of miles, commonly with a small stream
or even a river flowing through them. There may be wide and
lofty chambers wonderfully decorated with stalactites hung
from above or stalagmites growing up from the floor. These
structures are of lime deposited where drops of water con-
tinually drip from fissures in the limestone roof. The carbon
dioxide escapes in the open air of the cave, and the lime in
solution must therefore be deposited.
The most striking caverns known in Canada are the Namiku
Caves or Caves of Cheops on Cougar Creek, west of Glacier
in the Selkirks. More famous caves are found in other
countries, such as the Mammoth Cave in Kentucky, through
which one can walk for a number of miles. There are some
limestone regions, like the Karst in southern Austria, where
the whole drainage is underground, and where the rivers are
quite hidden except where some cavern roof has collapsed,
forming a sink hole.
THE WORK OF RUNNING WATER
The most active of the epigene agencies is running water,
which works almost everywhere on land surfaces, except
where it is replaced by the solid form, ice. In most deserts,
even, there is an occasional powerful flow of temporary
streams resulting from some sudden downpour; while in all
ordinary regions water flows permanently as brooks or creeks
or rivers, fed by rains and melting snows or springs or glacier
ice. The word "brook" has practically gone out of use in
central and western Canada, "creek" taking its place. The
distinction between creeks and rivers is very indefinite, the
small, easily-waded stream of the Don at Toronto being called
a river in Ontario, while the Kicking Horse, with a volume of
water like the Ottawa, is merely a creek in British Columbia.
The work of running water includes the transport of
materials, the cutting down of its bed, and finally, the deposit
of the materials transported. Fragments of rock lose from a
third to two-fifths of their weight in the water, which greatly
DYNAMIC GEOLOGY 75
aids transport. The work of transport and abrasion depends
on the rate of motion of a stream, and that depends on the
volume of water and the grade of its channel. Friction on
its bed counts for far more with a small stream than a large
one, so that a few inches of slope to the mile suffice to keep
a large river like the Nile or the Mississippi moving four or
five miles an hour, while a small brook may need a slope of
several feet per mile to cause the same rate of flow.
The part of the rainfall which flows off immediately gathers
into temporary rills which combine with others and presently
join some permanent stream; while permanent streams (creeks
or rivers) generally receive a part of their supply from springs
or lakes or the melting ice of some glacier.
WATERSHEDS AND CATCHMENT BASINS. Each river has its
own territory, draining all the water precipitated upon it
except the portion removed by evaporation; and the whole
of Canada has been divided up into drainage systems, tribu-
tary usually to some great river which carries its waters to
the sea. The amount of water which a river can deliver, say
for a city water supply or as a source of power at some water-
fall, will equal the rain and snowfall of the region minus the
evaporation; and in estimating the continuous supply avail-
able, one should take the amount of flow at the stage of
lowest water. The boundaries of these catchment basins or
drainage areas form watersheds, sometimes called divides or
heights of land.
Watersheds vary greatly in their character, being some-
times low and swampy, or even a lake which has an outlet
both ways, while, on the other hand, a sharp mountain ridge
may decide whether a raindrop shall go to the Atlantic or
the Pacific. One of the most notable divides in the world
extends along the southern Rockies between Alberta and
British Columbia, where tributaries of the Missouri, the
Saskatchewan, the Mackenzie, the Columbia, and the Eraser
rivers head not far apart, sending their waters to the Gulf
of Mexico, Hudson bay, the Arctic ocean, and the Pacific
ocean. One small pool, the Committee's Punch Bowl, on
Athabasca pass, sends a rivulet to the Columbia and another
to the Mackenzie, dividing its waters between the Pacific in
Lat. 46° and the Arctic ocean in Lat. 68°. The Columbia
76 ELEMENTARY GEOLOGY
snowfield feeds glacial streams whose waters reach the Pacific,
the Arctic, and the Atlantic oceans.
Where the headwaters of two rivers flowing in opposite
directions meet at a watershed, one of them may have a
steeper grade and a larger rainfall and so cut back faster
than the other, encroaching on its drainage basin and finally
"decapitating" it, thus taking possession of its upper valleys
and tributaries. This operation is sometimes called "piracy."
The headwaters of the Columbia illustrate this.
TRANSPORTING POWER OF RIVERS. The power of rivers to
transport materials varies as the sixth power of their velocity,
so that a rate of flow of half a mile an hour can transport
only sand grains, while at a mile an hour small pebbles can
be rolled along, and at two miles angular stones as large as
eggs. At more rapid rates large pebbles or stones can be
toppled over by the current and thus be moved slowly down-
stream. With one's head under water the stones can be heard
striking one another.
Angular stones thus moved along the bottom have their
edges broken off and presently become rounded pebbles, and
the pebbles grow smaller by the constant wear as they advance
down-stream. It is evident that the rocks forming the bed of
a swiftly flowing river, and especially of a mountain torrent,
will be constantly abraded by the rock fragments urged along
by the current. This cutting of the bed is called "corrasion."
Clear water alone does no work, since it is without tools for
the purpose; and streams carrying only fine particles, like
silt and sand, may polish the rock beneath but cut down
their bed only slightly.
The fragments of stone moved along the bottom of a
stream or carried in suspension are called its load, and with
a given rate of flow only a fixed amount of load can be trans-
ported. If a fully loaded stream reaches a wide part of its
channel with a gentler grade and the current slackens, some
of its load must be dropped. At such points its bed will not
be cut down, but will be filled up, and the stream is said to
aggrade its channel, while in other places it is degrading it.
TYPES OF WORK DONE BY RIVERS. In many rivers flowing
from mountains to the sea one can distinguish a swift upper
part with a steep grade, an intermediate part with gentler
DYNAMIC GEOLOGY 77
but irregular grades, and a part flowing through a flood plain
nearly at sea level. In the first part cutting and transport
are active and deep V-shaped valleys or even steep walled
canyons are being carved. Where there are eddies, stones
may be kept revolving as grinding tools and pot-holes may
result. In low-water seasons one may see the smoothly
rounded stones lying at the bottom of deep beautifully shaped
wells in solid rock. Pot-hole may succeed pot-hole ; the walls
between may be broken through and thus the channel is
FIG. 22. CANYON OF ABITIBI RIVER, ONTARIO
deepened fifteen or twenty feet. Pot-holes may be studied
along the Ottawa and other Ontario rivers.
Canyons, deep and long gorges cut with steep or nearly
vertical walls of rock, are scarcely found in the inhabited
part of eastern Canada, but are well displayed in the western
mountains, as along Thompson and Fraser rivers. The most
famous canyon in the world, that of the Colorado river, is
more than 300 miles long and in places more than 5000 feet
deep, and has been sawn through a slowly rising tableland
which is 7000 feet above the sea.
In its intermediate part the river may be cutting in some
places and filling in others, thus adjusting its grade.
In the flood-plain region, as the name suggests, the grade
is very gentle, the current slow, and in seasons of heavy rain
78 ELEMENTARY GEOLOGY
or melting snow the river may overflow its channel and spread
out over the lowlands. As it spreads out the current slackens,
and the mud which is being carried is deposited most thickly
on the banks of the river, but to a less extent in the shallow
lagoons on each side. This means that the floor of the wide
valley or plain is being slowly built up with finely ground
materials brought from above.
Since flood plains often supply rich soils and are thickly
peopled, the behaviour of rivers under these conditions
FIG. 23. MEANDERS IN FLOOD PLAIN, DON RIVER, TORONTO, ONTARIO
becomes of great practical importance, as in the Mississippi
valley. To prevent the damage done by floods, levees (em-
bankments) are built to keep the high water within the
regular channel, but when the flood slackens the mud which
would have been deposited on the plain is left on the floor
of the channel, raising it from year to year until some greater
flood than usual breaks the levees and inundates thousands
of acres. In northern Italy dikes or levees along the lower
reaches of the Po have been raised so high that the surface
of the river is above the roofs of the neighbouring villages.
MEANDERS. The flood plains are slowly rising by the addi-
tion of layer after layer of mud or silt, but the formation of
meanders tends, in the long run, to lower them. The river
DYNAMIC GEOLOGY 79
Meander in Asia Minor was famous with the Greeks for its
crooked channel and has given its name to the windings of
all rivers in their flood plains.
If a straight channel is dug through the alluvial deposits
of the plain for the use of the river, some obstruction, such as
a boulder or an undermined tree, deflects the current a little
toward one side, and there the bank is attacked and rapidly
carved away. Below this the current is now directed against
the other bank, with the same effect, and in the eddy on the
inner side of the bend mud and sand are being built up into
bars which are dry at low water.
This is an endless process, so that the curves grow more and
more extravagant until oxbow bends may come within a
short distance of one another. In the meantime the length of
the channel grows as the wriggling increases, and the slope
per mile grows less proportionately until an unusual flood
breaks across at some narrow neck between bends and an
"oxbow" is cut off, thus shortening the channel once more.
In this process a river may swing from one side to another
of its valley, lowering the whole width of the floor, usually
leaving on one or both sides a remnant of the former flood
plain as a terrace. This is called lateral planation, and in
course of time the plain is reduced more and more nearly to
sea level by the shifting of the meanders.
DELTAS AND ESTUARIES. The final destination of the river-
borne mud, silt, or sand is the sea or some inland lake. As the
flow of the river ceases when it enters the sea, the solids
brought with it are deposited, the work being aided by the
coagulating power of the salts of the sea; and a bar grows
up at its mouth if the sea is not too stormy or strongly tidal.
From time to time the river bursts a way through the bar
and begins a new one farther out, and so an amphibious
region is built out into the shallow water, gradually expand-
ing and often traversed by several channels or distributaries.
The flat islands thus formed are roughly triangular, like the
A (delta) of the Greeks, and the name delta, given to these
structures at the mouth of the Nile, is now generally used.
There are small deltas at the mouth of many rivers
in Canada, as that of the Kaministiquia at Fort William,
or of the Fraser at Westminster; and one very large, but
8o
ELEMENTARY GEOLOGY
unfortunately useless one, where the Mackenzie river enters
the Arctic ocean.
The greatest and most carefully studied delta of North
America is that of the Mississippi, which covers 12,300 square
miles and has a thickness of 630 feet at New Orleans. It is
constantly growing, since the river carries down solids enough
in a year to build up a square mile of sea bottom 268 feet.
Where a river enters a stormy or strongly tidal sea, the
load it delivers is quickly removed and spread out on the sea
bottom so that no delta is formed. Instead there is a funnel-
ARCTIC OCEAN
FIG. 24. DELTA OF THE MACKENZIE RIVER, ARCTIC OCEAN, AND OF THE
KAMINISTIQUIA RIVER, THUNDER BAY, LAKE SUPERIOR
shaped opening called an estuary where the tides boil in and
out, scouring the channel clean. Many seaports are formed in
this way, especially round the coasts of England. Ports in
New Brunswick and Nova Scotia along the Bay of Fundy are
largely of this type.
FEATURES OF YOUTHFUL RIVERS. An old river has had
time to grade its channel, forming a gradually steepening
curve from its mouth at sea level to its headwaters in some
mountain torrent ; but young rivers have not, and show many
irregularities because of the lack of adjustment. These
accidental features include falls and rapids and lake basins.
Practically all Canadian rivers except the Yukon, which is
only partly Canadian, have a very youthful aspect, since the
FIG. 25. EMPEROR FALLS, MOUNT ROBSON, BRITISH QQLUMBIA
82 ELEMENTARY GEOLOGY
work of the Ice Age blocked the old channels and forced the
drainage into new routes when the ice sheets were thawed
away. As a result our rivers have accidental channels, often
mere spillways from basin to basin, and there are falls
and rapids on almost all of them. Both of these youthful
features, lakes and falls, are of great practical importance
to the country.
Given time enough and rock fragments as tools, falls are
worn away and transformed into rapids, rapids lengthen out
and grow less steep, and ultimately a uniform grade is reached.
In the case of lakes, deltas niay be built out into them and
ultimately the basin may be filled, leaving only a marsh; or
the outlet may be cut down, partially draining the basin, so
that lakes also are ephemeral features of a river system.
THE ST. LAWRENCE— A YOUTHFUL RIVER SYSTEM
The Great Lakes with their connecting rivers ending in
the St. Lawrence provide a typical example of a youthful
river system. At its head is Lake Nipigon, 850 feet above the
sea, connected with Lake Superior by Nipigon river with
fine rapids and falls. Lake Superior, the largest area of fresh
water in the world, is 601 feet above the sea and is drained
by St. Mary's river into Lake Huron with a descent of 22
or 23 feet, of which 18 occur at the rapicls of Sault Ste. Marie.
Lake Huron is joined to Lake Erie by the St. Clair and Detroit
rivers, having only a slight fall. Niagara river connects
Lake Erie (575 feet) with Lake Ontario (246 feet) and in-
cludes miles of quiet water, tremendous rapids, and the Falls
of Niagara, having a vertical drop of 160 feet.
Niagara Falls has some unique features. It has lasted as a
vertical fall for thousands of years, beginning at the escarp-
ment near Queenston and cutting its way back six and a
half miles to its present position. The reason for this is found
in the character of the rocks of the escarpment, hard dolo-
mitic limestone on top and mainly soft shale beneath. The
shale is easily attacked by the eddying waters and is undercut.
From time to time blocks of the overlying limestone are
undermined and fall, to be whirled as missiles against the
shale beneath, helping on the work of recession.
FIG. 26. MOUNTAIN TORRENT, NAKVAK, LABRADOR
84 ELEMENTARY GEOLOGY
From Lake Ontario the St. Lawrence flows with many
rapids and a total fall of 246 feet to the Gulf of St. Lawrence.
All of the Great Lakes except Lake Erie reach depths below
sea level, so that they never can be drained by cutting down
their outlets, and the rivers flowing into them bear little
sediment, so that the process of filling them with delta
materials would be enormously long. From the human point
of view the system is very permanent.
The Great Lakes and the rivers joining them have had a
powerful influence on the life of the adjoining regions. The
lakes with their connecting canals permit navigation to the
heart of North America, while the falls and rapids on the
rivers furnish power to all the cities within reach. A scarcely
noticeable part of the water of Niagara Falls supplies Buffalo,
Toronto, and a dozen smaller cities with light and power; and
a new installation utilising a fall of 300 feet will soon almost
double the amount of power available.
Many other Canadian rivers have similar conditions, though
on a smaller scale. The youthful character of the rivers of a
country is evidently a matter of great economic importance.
It is perhaps worthy of note that each section of river
linking two of the lakes has a separate name, as the Nipigon,
the St. Marys, etc., though the whole chain makes up a
single drainage system, that of the St. Lawrence. The
Mackenzie and the Nelson also change their names above
lakes on their course.
PENEPLANATION. Rivers and their tributaries are continu-
ally cutting down their valleys toward base level, and as a
result the hills or mountains forming the watersheds are
slowly lowered, the grades becoming more and more reduced
even at the headwaters, and the country becoming approxi-
mately level with only gentle elevations between the drainage
areas of the sluggish rivers. If the process were carried to the
eid a real plain might result, but so far as known this stage
has never been reached. The nearly level surface attained,
with only slight slopes and low hills or ridges, has been called
a peneplain (almost plain) .
Peneplains mean, of course, that the region has remained
stationary for an immense length of time, since any rising or
sinking of the land as compared with sea level would interrupt
DYNAMIC GEOLOGY 85
the process. An important rise of the land would rejuvenate
all the rivers, which would begin a new "cycle of erosion"
and start the work of destruction all over again.
It is believed that the Pre- Cambrian region of Ontario and
Quebec is an example of a peneplain which has been elevated,
so that all the rivers flowing outwards have many waterfalls
and a descent of hundreds of feet on their way to Lake
Superior or the St. Lawrence. The region is not now level,
but is made up of low hills and shallow valleys. Looking out
from a hill top one usually sees that all the hills in sight rise
FIG. 27. WAVES, NEWCASTLE, NEW SOUTH WALES
to the same flat skyline, that of the original peneplain. A
rare residual hill rising distinctly above the rest because it
resisted erosion better is called a monadnock, from a mountain
of that kind in the eastern United States.
THE WORK OF SEAS AND LAKES
In standing water, work of geological importance may be
done in three ways — by waves, currents, and tides; but in
the smaller bodies, such as lakes, only waves are of much
consequence.
DESTRUCTIVE WORK OF WAVES. Waves are undulations
of the water caused by wind, and as these undulations do
86
ELEMENTARY GEOLOGY
not usually go to great depths, their effects are noticeable
only in shallow water and on the shore. As a wave approaches
the shore its lower part is hampered in its motion and the
upper part tends to topple over as a breaker. The dashing of
breakers is a powerful mode of attack resulting in destruction
of the shore, forming a cliff where the land is high and removing
and assorting the debris to form a beach. Coarser fragments
are piled up near the foot of the cliff, while the undertow of
Photo, by Professor Clarkson
FIG. 28. WAVE EROSION, CAPE BLOMIDON, NOVA SCOTIA
the wave by which the water dashed up, returns to its proper
level, drags sand and mud back with it, distributing them on
the bottom. Since waves rarely strike the shore squarely, but
usually at an angle, the materials of the beach will be shifted
along shore in the direction toward which the wind is blowing.
For example, where the effective storm winds come from the
east the beach materials will slowly march westwards.
The destruction of the shore is largely effected by the
undercutting of cliffs, slices slipping down from time to time
and the materials being worked over by the waves as sug-
DYNAMIC GEOLOGY
87
gested above. This means the recession of promontories
under wave action. The cliffs at Scarboro near Toronto
are receding at an average rate of 1-62 feet per annum;
and on the stormy coasts of England the shore has in
places receded for hundreds of yards or even miles within
historic times.
CONSTRUCTIVE WORK OF WAVES. On the other hand, the
gravel and sand urged along shore by waves from the direc-
tion of the prevalent storm winds are built out into the next
bay, forming a spit. If the bay is shallow the spit may
LAKE ONTARIO
FIG. 29. A HOOK. THE "ISLAND" AT TORONTO, ONTARIO
gradually extend across its mouth, forming a bar, perhaps
completely cutting it off as a separate body of water. This is
shown at Hamilton bay at the western end of Lake Ontario,
which is enclosed by the bar called Burlington Beach. Where
the bay is deep the spit extends only as far as shallow water
will permit and then bends inwards as a hook. In time hook
after hook will be built into the deeper water, perhaps forming
a considerable area of land with unfilled lagoons between the
separate advances. Toronto island is a good example of this.
Either a bar or a hook may enclose a well-sheltered harbour
and serve as the starting-point for a city.
The new land built by the waves can never rise higher than
wave-work permits, on Lake Ontario about five feet above
88 ELEMENTARY GEOLOGY
water level, and often much larger areas, called shoals,
remain under water.
The general effect of waves is to smooth out the irregu-
larities of shores, cutting off promontories, and stretching
bars across bays. This is well seen on the shores of Prince
Edward island and in other regions on the Atlantic coast. A
shore is said to be young when its outline is ragged, and old
when wave-work is nearly complete.
A change of level may transform an old shore into a young
one, as along our Atlantic coast where the land rose after the
Ice Age. Depression often provides harbours, like that of
Sydney in Australia.
OCEAN CURRENTS. Currents in lakes are not of much
geological importance, but ocean currents may have much
significance, especially as affecting climates and the geo-
logical forces depending on climate.
The most important currents are caused mainly by prevalent
winds, particularly the steadiest of all winds, the trades. As
these north-easterly and south-easterly winds constantly urge
the waters of tropical seas westwards, a surface drift is set
up in that direction. In the case of the Atlantic this drift
impinges on the north coast of South America and is bent
north-westwards into the Caribbean sea and then into the
Gulf of Mexico, where the waters are entrapped. After
doubling back to the south-east the waters escape as a well-
marked current, "a river in the ocean," round the end of
Florida, and follow the coast to Cape Hatteras. From this
point the warm water of the Gulf Stream spreads out over
the surface and loses the character of a definite current, but
gradually makes its way north-east across the Atlantic as a
surface drift. Part of the water turns southwards, completing
the circle round the vast eddy of the Sargasso sea, part
moves northwards along the European coast, reaching the
Arctic ocean and even touching north-western Russia. Iceland
feels its effects and a tongue touches the south-west side
of Greenland.
On the other hand, a return current of icy water laden with
bergs comes down from Davis strait along the coast of
Labrador to Newfoundland and bends westwards past Nova
Scotia to New England.
go ELEMENTARY GEOLOGY
The climatic effects of the Gulf Stream and the Labrador
current are most striking. Northern Labrador is treeless and
arctic, with only two or three months of foggy and chill
summer in the year, while the corresponding coast of Europe
includes the comparatively mild regions of Scotland and
southern Norway. Harbours are open all the year as far north
as Hammerfest, well within the Arctic Circle, while the
harbour of Quebec, far south of London, is closed for five-
months. The same relation seems to have held during the
Ice Age, for the European ice sheet reached Lat. 52° only,
leaving the southern edge of England uncovered, while the
Labrador sheet in America reached Cincinnati in Lat. 38°.
On the Pacific coast the Japan current produces much the
same effect as the Gulf Stream, giving a mild climate even in
southern Alaska. Prince Rupert in Lat. 54° is never blocked
by ice, and the summer isotherms of northern Alberta and
British Columbia bend away to the north. The contrasts
between the climates of the Pacific and Atlantic coasts of
Canada are almost as striking as those on the two sides
of the Atlantic.
In the southern hemisphere the cold Humboldt current
brings a temperate climate along the western coast of South
America to within three or four degrees of the equator; but in
general, ocean currents are of less importance than in the north.
TIDES. Even on great lakes, like Superior, tides are insigni-
ficant, but on many sea coasts they are prominent geological
factors. In a general way tides are caused by the differential
attraction of the moon and sun on the water of the ocean and
on the earth as a whole. The sea on the side towards the
moon is 4000 miles nearer than the centre of the earth and
is therefore pulled toward it; while on the opposite side it
is 4000 miles farther away than the centre of the earth and
so is left behind. Thus two tides are caused by the attraction
of the moon, one on the side towards it and the other on the
side opposite. The same is true of the sun but on a smaller
scale, since the sun is so much farther away. The highest or
"spring" tides occur when the moon and sun are either on
the same or on opposite sides of the earth, and the lowest or
"neap" tides when they are at right angles to one another
and pulling at cross purposes.
(a)
00
FIG. 31. TIDE AT WOLFVILLE ON BAY OF FUNDY
(a) In. (b) Out.
92 ELEMENTARY GEOLOGY
In the open ocean the tides average from four to six feet,
but on many shores where funnel-shaped bays lead inland
they are compressed and become much higher, as at Quebec,
where they reach fourteen or eighteen feet. On the Bay of
Fundy and at Cape Chidley at the north end of Labrador,
tides may rise forty or fifty feet or even higher under special
circumstances and do a large amount of work.
It might be supposed that the west side of America would
be sheltered from the tides, but when the great oceans are
stirred by these motions they spread in all directions and are
almost as marked in Vancouver Harbour as at Quebec.
Twice a day the tide advances upon the land and then
recedes. In narrow bays like Fundy it rushes in as a powerful
current and even moves as a low wall of water far up rivers,
causing a "bore." This is well seen at Moncton.
These inward and outward motions stir up the mud in
shallow waters, making the sea red instead of blue along the
Fundy shores, and evidently scour the bottom and transport
mud to the deeper water off shore.
Tidal currents between islands and the mainland, as at
Seymour Narrows north of Vancouver, may be so powerful
that vessels cannot make headway against them and must
anchor till they change. It is proposed to use the Fundy tide,
rushing between an islet and the shore near Cape Blomidon,
as a source of power, the main difficulty being that the current
is reversed every six hours. To make use of tidal power means
setting to work part of the energy of rotation of the earth.
In Evangeline's country the great tidal meadows are diked,
and by admitting the tide at high water and allowing it to
deposit its mud before releasing it, the surface has been
built up to higher levels in the region of Grand iPre.
There can be no doubt that tidal friction serves as a
brake on the rotation of the earth and is very gradually
lengthening the day.
THE SALTS OF THE SEA. The saltness of the sea is one of its
most striking features and, is of great interest geologically.
As all rivers which flow to the sea carry down various salts
in solution, while the water evaporated from the sea is pure,
it is evident that the salts must accumulate from age to age.
The length of geological time has even been calculated at
DYNAMIC GEOLOGY 93
about 90,000,000 years by dividing the annual increment of
sodium as brought in by rivers into the total amount of sodium
contained in the salts of the sea.
If 100 pounds of sea water are evaporated about 3! pounds
of solids remain, nearly 78 per cent, being sodium chloride,
ii per cent, magnesium chloride, giving sea water its bitter
taste, and the rest various salts in smaller amounts, including
sulphates of magnesium, calcium, and potassium. It seems
curious that the commonest substance in spring or river
water, calcium carbonate, is present only in very small
amounts; but this is accounted for by the work of marine
animals and to a less extent plants, which are constantly
removing it to build shells, coral, etc.
The salts are very uniformly distributed through the open
sea, analyses showing practically the same amounts wherever
the samples are collected, even when taken from great depths
when sounding, and it is certain that there is a great but slow
system of circulation keeping the waters thoroughly mixed,
the cold arctic waters sinking and travelling towards the
equator, while the warm equatorial waters spread super-
ficially toward the poles. Even under the equator the water
at great depths is not more than a degree or two above
the freezing point.
This circulation carries down oxygen in solution also,
providing for the needs of the deep-sea animals and removing
the carbon dioxide formed by their breathing.
While the salts of the sea are constantly accumulating there
are means also by which they can be removed. If a bay
is cut off by a bar or by a change of level of the bottom
in a region of desert climate, the water will be evaporated
and a bed of salt deposited. This process may be repeated
several times, forming bed after bed of salt separated
by shale or impure limestone, as in the salt region of
south-western Ontario.
DEPOSITS IN SALT LAKES. Similar deposits are formed in
inland regions with a dry climate where rivers supply salts in
solution to lakes without outlets; but the salts may vary
greatly in character according to the soluble materials
contained in the soils through which the rivers flow.
In Canada lakes without outlets are found in the drier
94 ELEMENTARY GEOLOGY
parts of Saskatchewan, Alberta, and British Columbia. Some
of these lakes, such as the Quill lakes and Old Wives lakes,
are extensive and have several streams flowing into them,
but are not heavily charged with salts. In western Canada
lakes of this kind are usually called alkaline, though most
of them contain only neutral salts, such as sodium or mag-
nesium sulphate. A few are actually salt lakes charged with
common salt. In central British Columbia there are several
small lakes containing special salts, some having practical
value, like the deposits of hydromagnesite near Clinton and
FIG. 32. BORAX LAKE AND THE VOLCANO OLLEGUE, BOLIVIA
at Atlin, and the ponds with epsomite and sodium carbonate
near the former place.
More famous salt lakes occur in countries having actual
deserts. For instance, Great Salt lake in Utah is a saturated
solution and is depositing salt, and the Dead Sea of Palestine
is of the same kind. Dried-up lakes on the tableland of
Bolivia are white with borax, and several other salts are
deposited in desert lakes in different parts of the world.
MARINE DEPOSITS. Gravel, sand, and mud derived from
the attack of waves on the shore or brought in by rivers are
deposited in the shallow waters offshore; but " terrigenous"
deposits, as these are called, play only a small part in the
deposits of deeper seas. Beyond the shelf bordering the
DYNAMIC GEOLOGY 95
continents, often for a width of 150 or 200 miles, the
bottom sinks rapidly to great depths, reached only by the
finer muddy products or by volcanic ash or pumice. With
these materials there are innumerable microscopic shells of
foraminifers, forming a greyish ooze. Below 2000 fathoms
there is sufficient carbon dioxide present to dissolve shells
formed of lime, and the abyssal deposits below this are
formed with extreme slowness. Siliceous shells, small con-
cretions of oxide of manganese, teeth of sharks, and
ear-bones of whales, the most resistant parts of their
structure, may be dredged from even the deepest seas.
There seems to be a small amount of life existing at even
the greatest depths in total darkness and a nearly freezing
temperature, the organic matter slowly settling to the bottom,
from the death of creatures near the surface, supplying the
necessary food.
THE WORK OF SNOW AND ICE
Water in the solid state appears as skeleton crystals in
snow and also in the massive form as ice. Snow entangles
much air in its descent and thus forms a non-conducting
covering for the earth, practically putting an end to epigene
work for the time. Snow may also be considered a reservoir
of water which is discharged when the thaw comes in spring.
Most Canadian rivers have their greatest floods then, and do
more work in the time of melting snows than in all the rest of
the year. The annual floods of the Thames and Grand rivers
illustrate this.
Most rivers and all but the largest lakes freeze over in
winter in our climate, sometimes to a thickness of two or
three feet. The ice covering a lake expands with a rising
temperature like any other solid, and may push boulders
outwards along the shore, sometimes forming a kind of wall
or rampart in this way, as at Lake Simcoe.
Rocks frozen into the ice along shore may be rafted off
when the ice breaks up, and afterwards may be left stranded
at some other point. The large blocks often piled on exposed
points in the Thousand islands, River St. Lawrence, have
been transported in this way. Ground ice formed at the
96
ELEMENTARY GEOLOGY
bottom of rapid rivers, as in the Hudson Bay region, may
also float off boulders to be dropped when the ice melts
with the advance of spring.
GLACIERS. The most important work of ice is done, however,
in places where snow lies permanently, as on high mountains
or in the Arctic regions. In all parts of the world, even under
the equator, there is an altitude above which the snow does
not melt in summer. This level is called the snowiine, and it
is fixed partly by the temperature and partly by the amount
of snowfall. In southern Canada perpetual snow is found in
FIG.. 33. ICE RAMPART, LAKE SIMCOE, ONTARIO
the eastern Rocky mountains at about 9000 feet and in the
western Selkirks at 7500 feet, the latter facing .the Pacific
and having a snowfall often reaching from thirty to fifty feet
per annum. Farther north the snowiine lowers, while toward
the equator it rises and sometimes reaches 16,000 feet or
more in the tropics.
From steep slopes the snow may slide down bodily into the
valleys, especially toward spring, sweeping everything movable
with it and mowing down forest trees in its path. The Canadian
Pacific Railway has built many miles of snowsheds to protect
its line from such snowslides or avalanches. In most cases,
however, the slopes above snowiine are not steep enough for
slides, and the snow heaps up year after year until hundreds
DYNAMIC GEOLOGY
97
of feet may accumulate. Permanent snow receives the name
of neve from the Alps where glaciers were first studied.
The pressure of overlying snow and a small amount of
melting and freezing gradually turn the lower layers into ice
which generally has a distinct stratification. The ice thus
Photo, by A.O. Wheeler
FIG. 34. GLACIER ON MOUNT BALFOUR, ROCKY MOUNTAINS, SHOWING
NEVE FIELDS, ICE FALLS, AND MEDIAL MORAINES
formed moves down below the snowline into the valley and
is called a glacier, which ends where the rising tempera-
ture at lower levels thaws the ice as fast as it descends.
As the whole ice field tends to pull away from the sides of
the valley, an irregular gap is left round the upper edge,
called a " bergschrund."
The motion of a solid substance like ice merely under the
G
98
ELEMENTARY GEOLOGY
pressure of its own weight is not easily explained, though the
fact of "regelation" aids in its movements. Water expands
when freezing, unlike almost all other substances, so that
pressure lowers the freezing point, and where the pressure is
greatest the ice may change to water, which slips to a point
of less pressure and becomes solid again. Glaciers are made
up of separate grains or small individual masses of ice which
can move among themselves under pressure and become
re-cemented when the pressure slackens; and glaciers can
FIG. 35.
Photo, by Byron Harmone
ICE CAVE AND RIVER AT END OF YOHO GLACIER, BRITISH
COLUMBIA
adjust themselves to changes of grade by breaking across,
also, forming crevasses, great fissures often extending to the
bottom. When the obstruction is past, regelation comes into
play and the ice becomes solid once more. On steep irregular
descents the glacier is often broken up into ice pinnacles
called semes, which disappear, however, lower down.
The flow of glaciers is like that of a plastic body, such
as pitch, and their motions are very slow, usually not more
than one foot a day and never more than sixty feet. The
centre of a glacier moves faster than the edges owing to
friction on the floor of the valley.
DYNAMIC GEOLOGY
99
As the ice is solid, any rocks or .debris slipping down from
the cliffs alongside are carried down on its surface as " lateral
Photo, by Melson
FIG. 36. MEDIAL MORAINE, ALASKAN BOUNDARY
moraines." When glaciers meet, the two adjoining lateral
moraines join to make a "medial moraine"; and where the
FIG. 37. TERMINAL MORAINE, MAIN GLACIER, MOUNT ROBSON, B.C.
ice finally melts, all the transported material is dumped in a
crescent-shaped ridge called a " terminal moraine."
TOO
ELEMENTARY GEOLOGY
FIG. 38. BOULDER CLAY
STONES, TORONTO, ONTARIO
Work is also done beneath the ice, where all loose bits of
rock are frozen in and used as chisels and gouges, while
the finer stuff serves as
sand-paper and polishing
^^^^PPK^BHIM^ i P°wder- The mass of
i&$3mbmit?mmBmrm rocks and finely ground
"rock flour" dragged
along in the lower part
of the ice is left behind as
boulder clay or till when
the ice melts. Many
/^f flip t;tonp^ in tVif*
j/ r\ .' £*' J ;* ***,'* j^. ^ *-» ' it f"V **%'*• \H£** 4Jfci^^M«v ^fJ'-'tSi Liiv./ OL\-Fiivo ill im*
r ^.^*jfcsJiiiyil26Sif^x S?^'f clay have their corners
blunted and have smooth
faces ground upon them,
which may be scratched
WITH STRIATED by hard projecting points
as they are forced along.
Such stones are called soled boulders or striated stones, and
are very characteristic of ice action, since no other agency
produces such effects. Scattered stones left after the glacier
melts are called erratics.
The rock surface beneath the ice also may be polished and
striated, and hills of harder
rock may have rounded
forms on the side from
which the ice advanced, and
are called roches moutonnees
(sheep rocks) . In the lee of
such hills of rock boulder
clay or loose debris may
be protected, giving the
arrangement called crag
and tail.
Since glaciers move so
slowly as compared with
water, to drain a given area FIG. ^ 39
they must have an enor-
mously greater channel. Accordingly the former V-shaped
river channels are enlarged and carved into wide and deep
STRIATED STONE FROM
BOULDER CLAY AT TORONTO, ONT.
DYNAMIC GEOLGGYJ: ioi
U-shaped valleys when ice occupies a region. Finally, small
mountain glaciers hollow for themselves armchair-like nests
called cirques. All of the features mentioned above are well
seen in the Rocky mountains below the present level of ice
action, and all but the U-shaped valleys and cirques are
typically shown in eastern Canada as a result of glaciation
in the Ice Age. Where a U-shaped valley has sunk below sea
level it forms a long narrow inlet called a fiord. The ragged
outlines of the coast of British Columbia, Labrador, and other
regions once glaciated illustrate this feature excellently.
FIG. 40. ROCHE MOUTONNEE AND STRIATED SURFACE, COPPER CLIFF,
ONTARIO
ICEBERGS. Where glaciers reach the sea, masses of ice break
off and float away as icebergs. These may be of all shapes
and sizes, some in the Antarctic regions even reaching several
square miles in dimensions. Any morainic material upon the
ice is carried along by the icebergs. Thousands of bergs
"calved" from the Greenland glaciers are carried in long
processions southwards by the Labrador Current, at the
rate of about a mile an hour. These often reach the Banks of
Newfoundland and get aground there, where the warmer air
and water rapidly melt them, dropping their load of clay and
stones upon the banks, which are being built up of materials
freighted from Greenland, a thousand miles away.
102
ELEMENTARY GEOLOGY
A few of the bergs go still farther south and get into the
path of the transatlantic steamers before finally melting.
DRIFT DEPOSITS
The whole series of deposits formed by ice and by the
glacio-natant waters — waters coming from the marginal melting
of the ice sheets — is called drift. The greater part of Canada
is covered by drift, those areas which were not worked over
FIG. 41. CIRQUE NEAR MOUNT TETRAGONA, LABRADOR
by ice being called driftless. The largest area of the kind in
Canada is in Yukon territory ; but the higher parts of British
Columbia escaped ice action, and a few thousand square
miles in the far north-east of Labrador, on the Torngat table-
land, are also driftless. In southern Canada only a small area
above 2500 feet in the Shickshock mountains of Gaspe
shows no signs of ice action.
In most parts of Ontario and Quebec the present surface
of the country still preserves the characteristic landscapes
left by the great ice sheets which vanished thousands of years
ago ; and, as mentioned earlier, the arrangement of lakes and
rivers is closely related to the work of the ice.
DYNAMIC GEOLOGY 103
THE ATMOSPHERE
Air and water are close partners, and several results of
atmospheric work have been mentioned, such as weathering
and the causing of waves and currents.
The air consists essentially of two gases, nitrogen and
oxygen, with a variable amount of water vapour. The specific
gravity of dry air is about 14^ as compared with hydrogen,
and that of the gaseous form of water is 9, so that water
vapour is the lighter of the two. The weight of the atmosphere
at sea level is about 14 pounds per square inch, or equivalent
to a column of mercury 30 inches high. At 18,000 feet above
the sea its weight is only half as much. The upper limit of the
air is vague, since the gases grow rarer until, at about 100
miles, they are no longer dense enough to cause meteors to
glow by friction.
The pressure of the air is constantly changing, partly by
variations of temperature and partly by the evaporation of
water or its precipitation as rain or snow. Expansion of the
air by heat causes it to rise, while colder air comes in to take
its place, producing winds.
The most uniform of winds are the trades of the tropics,
caused by the ascent of warm, moist air under the effect of a
vertical sun. As the air sucked in from north and south
comes from regions of less motion of rotation than at the
equator, where the surface travels 1000 miles an hour, these
winds appear to lag and move in diagonal directions, becoming
respectively north-east and south-east trades. As the air
brought in by the trades comes from cooler latitudes and is
warmed up as it approaches the equator, the trade winds
themselves are dry, though the zone of calms, the doldrums,
where they almost meet, is excessively rainy.
Other important but more local winds called monsoons are
seasonal, blowing inwards toward heated tropical lands in
summer and outwards from the cooler continent toward the
warmer seas in winter. Many parts of India are dependent
on the rains brought by the monsoons for their agriculture,
and a failure of the monsoon means famine.
In temperate regions the great cyclonic storms, such as
those which cross Canada from west to east, are of most
104
ELEMENTARY GEOLOGY
importance, though the west or north-west winds, which blow
more commonly and are sometimes called the anti-trades,
have much effect on the winter climate.
One strongly blowing west wind, crossing the mountains
of British Columbia, and becoming warm and dry by compres-
sion as it descends thousands of feet to the foothills and
prairies of Alberta, is famous as the chinook, which licks off
i ..
FIG. 42. SAND DUNE NEAR WELLINGTON, ONTARIO
the winter's snow and renders possible the cattle and horse
ranches of the region.
/>WoRK OF THE WIND. On dry land the commonest work of
wind is the lifting and transport of dust, familiar everywhere.
In desert climates this becomes of great importance, and
immense quantities of fine rock particles travel in the direction
of the prevalent winds. In moister regions where there are
streams and pools and vegetation this dust is halted and
builds up a soft, unstratified rock called loess, the best example
being found in China, where dust from the desert of Gobi to
the east has formed in places hundreds of feet of loess.
DYNAMIC GEOLOGY
105
Wind has one advantage over water as a transporting agent,
since it can carry its load up-hill and remove it completely
even from an enclosed basin, whereas water can only work
downwards and can do no work below its base level. The
winds can lift and carry bodily small dust particles, but
grains of sand are too heavy to be carried in this way by
ordinary winds, so that the grains are only lifted a few inches
and then dropped. By constant repetition great masses of
sand are thus moved, forming dunes.
FIG. 43. BAD LANDS SHOWING WIND SCOUR, RED DEER RIVER, ALBERTA
Dunes are shifting hills, advancing in the direction of pre-
valent dry winds. When wet the wind has no power to lift
sand. The most perfect dunes are naturally found in deserts,
e.g. in Nubia or Peru, and take the form of a crescent or
horse's hoof, with its outer curve facing the prevalent wind.
On that side a low stream of sand grains may be seen dancing
upwards to the crest and then dropping in the eddy which
forms a steeper slope on the inner face. The surface of the
sand is rippled. Such regularly formed desert dunes are
sometimes called barchans.
Sand dunes are to be seen near Wellington in Prince Edward
county, Ontario, on the north shore of Lake Erie, and at
106 ELEMENTARY GEOLOGY
many other places. They are sometimes serious invaders,
covering fields and orchards and even houses. In the Old
World they have been conquered by planting certain kinds
of grasses, followed by pine trees.
Winds do important work also in scouring and wearing
down by a sort of sandblast action all rocks exposed to driving
particles in desert regions. Egyptian monuments facing the
desert often have their inscriptions destroyed in this way;
but good examples are not found in Canada.
One effect of the work of dry, powerful winds is the drifting
of the lighter soils from the fields in southern Alberta. This
soil-drift, as it is called, is a serious menace to the wheat-fields
near Lethbridge, Alberta. The thin prairie sod protects the
sandy soil beneath, but when broken and not covered by a
crop the whole surface may be blown away by a strong
west wind, so that the air for miles to the east is thick
with dust particles.
LIFE AS A GEOLOGICAL FACTOR
Life is closely bound up with water and air and also with
sunlight, since all the food of the world originates in the work
of plants containing chlorophyll. For at least part of the year
water must be in the liquid form if life is to continue, so that
a suitable temperature is necessary also. The individual
living being is insignificant, but the power of multiplication
makes some species of great importance as rock formers.
Both plants and animals have a part to play and will be
referred to.
GEOLOGICAL WORK OF PLANTS. SOILS. Plant life exists in
some form in almost every part of the world except on wide
snowfields and a few of the driest deserts, such as the nitrate
region in Chile. The relation of plants to soils is a fundamental
one and may be considered first. Most soils consist of a basis
of finely divided mineral matter mixed with humus, the
product of decaying plant remains, a good soil containing
from 5 to 20 per cent, of organic materials. The mineral
basis of a soil may be sandy, clayey, etc., and should con-
tain supplies of indispensable chemical elements, especially
phosphorus, potash, lime, and sulphur.
DYNAMIC GEOLOGY 107
The beginning of soil production in a new region, e.g. one
just freed from a sheet of ice, is generally made by the growth
of wind-borne lichens, since the lichen is a very efficient
partnership of a fungus with an alga, the latter supplying
food and the former attending to outward relations. The
death and decay of lichen after lichen prepares the way for
wind-borne spores of mosses, and the mossy sponge gives
lodgment for ferns and bird-sown, berry-bearing plants,
followed by trees with winged seeds. Ultimately a consider-
able thickness of humus is built up.
The decay of roots affords some mixture of organic with
mineral matter in the soil, but the aid of earthworms or
burrowing mammals, such as the mole or the western gopher,
is necessary for the proper stirring up of the soil ingredients.
Protective Work of Plants. Once a soil is prepared in most
temperate climates a covering of grasses and other low-grow-
ing plants forms a sod or turf, or else forest spreads, protecting
the soil from wind or rain erosion. It is interesting to note
that the "bad lands," almost useless because so completely
gullied and scoured by rain, are found in regions of low rain-
fall, .since the water supply is not sufficient for a complete
mat of grasses, while the well-protected prairie with larger
rainfall scarcely suffers at all in this way.
The protective effect of forests is well known. They specially
regulate the run-off of rain and the sudden thawing of snow,
thus spreading the flow of water more evenly over the year.
Many mill streams used in Ontario in earlier, better wooded
days now dry up in summer, and in several countries forest
land is preserved at the headwaters of important rivers, to
regulate their flow. The forest lands of the foothills and
mountains in Alberta have been reserved by the government
largely to protect the headwaters of the rivers which flow
eastwards into the plains.
Rock Formation by Plants. A number of plants secrete
hard parts which accumulate to form beds of rock. The deli-
cate siliceous shells of diatoms are good examples of this,
forming beds of diatom earth on the bottom of lakes, as in
Muskoka. This material is of some value as an abrasive.
The formation of travertine and of bog iron ore beds is
largely due to mosses and other plants removing carbon
io8 ELEMENTARY GEOLOGY
dioxide from the solutions of lime or iron compounds, thus
depositing them about themselves.
In the sea, nullipore seaweeds (Lithothamnion, etc.) secrete
carbonate of lime and may form great masses of limestone,
usually in partnership with marine animals ; while chara and
other plants help in depositing marl in fresh waters.
The mangrove tree, growing densely along protected shores
in the tropics and sending down aerial roots in all directions,
fixes the mud brought by the tides and slowly extends a
slimy, foul-smelling margin of land into the shallow sea.
Fossil Fuels. Much the most important geological work of
plants from the economic side is the storing of their own
tissues in bogs or shallow water as peat, which may later be
transformed into coal. The growth of peat may be studied
in many places in all the provinces of Canada, the Indian
term, muskeg, being generally used instead of the Old World
name, bog.
Certain mosses, especially sphagnum, are active in this
work, but many other swamp plants take a part in it, and
the leaves and branches or trunks of trees near by may also
be enclosed in peat. While plant tissues decay completely
on dry land, under water in the presence of tannin formed in
the bog the decay takes a different course and is much less
complete. The main change going on is the escape of two
gases, carbon dioxide, and methane or marsh gas, a com-
pound of carbon and hydrogen, diminishing the amount of
oxygen and hydrogen present. Thus peat changes from a
pale brown on top of the bog to black muck at the bottom,
the latter being richer in carbon and poorer in oxygen and
hydrogen compounds.
But for the fact that peat clings tenaciously to the last
25 or 30 per cent, of water, so that it cannot be dried beyond
that stage by ordinary means, it would provide a most
excellent fuel.
Materials originally like peat but buried for long periods
of time advance farther in the loss of gases mentioned, and
form lignite, which generally retains from 15 to 30 per cent, of
water. Sub-bituminous coal comes next, containing less water,
and finally true bituminous coal, with very little water and
55 or more per cent, of fixed carbon, the rest consisting of
DYNAMIC GEOLOGY 109
hydrocarbons which burn with a yellow smoky flame. Where
mountain-building stresses cause folding of the beds of bitu-
minous coal, most of the remaining hydrocarbons pass off
and anthracite or hard coal remains, containing 80 per cent,
or more of fixed carbon and so little volatile matter that it
burns with a blue smokeless flame. Anthracite is the rarest
variety of coal and is nowhere commonly used except in the
eastern United States and Canada, and the known supply
may not last for more than a generation longer.
Practically all types of coal, from low-grade lignite to
semi-anthracite, occur in Alberta and British Columbia,
where all stages of change are found to be related to the
amount of disturbance and folding of the enclosing rocks,
lignite occurring in flat, undisturbed beds and the higher
grades where mountain-building forces have been at work.
GEOLOGICAL WORK OF ANIMALS. The geological work
done by animals consists chiefly in bequeathing their hard
parts for the formation of limestones, a work in which most
of the types of animals except the highest, the vertebrates,
are of some consequence. Two very low types, the protozoons
and the polyps, are particularly efficient.
Foraminifers. Many of the unicellular animals form shells
of lime, through which there are many little pores or openings
for pseudopodia, thus justifying the name foraminifer; and
most of them cluster in small colonies, like Globigerina. Their
minute shells accumulate in vast numbers on certain sea
bottoms as a greyish ooze, which ultimately may be con-
solidated to limestone, particularly the soft variety called
chalk. The white cliffs of Albion are of chalk which consists
mainly of foraminiferal shells.
Along with the lime-secreting protozoa there are, in smaller
numbers, some which build their shells of silica. These with
the siliceous spicules of slightly higher animals, the sponges,
may form siliceous beds. Usually, the silica is aggregated into
nodules or concretions, as flint in chalk, while in older lime-
stones the result is chert, which differs little from flint. Most
foraminifera are of microscopic size; one group, the num-
mulites, however, grew to be quite large, their flat shells reach-
ing the size and shape of a coin, which suggested the name
"coin animal." Their shells were deposited on a tremendous
no ELEMENTARY GEOLOGY
scale in the Mediterranean region during Eocene times,
forming widespread nummulitic limestones, some of which
have been built into the famous pyramids near Cairo.
Corals. Among the most impressive rock builders are
the polyps which secrete coral, but their work, except on
a minor scale, is confined to warm climates (68° F. as a
minimum) and clear seas, within a depth of about 150 feet.
Under these conditions corals of numerous species, aided
by some other animals, as well as nullipore algae, build
massive reefs either along shore, as fringing reefs, or separated
from the shore by a channel, when they are called barrier
reefs. When a reef surrounds a lagoon, either with or without
islands, it is called an atoll.
The corals do not build up a solid mass of rock, but the
waves break off and grind up projecting corals, filling in the
spaces and cementing, the whole solidly together. One or
more openings permit the movement of tides and currents
through barrier reefs and atolls, and the coming-in of a river
with fresh and muddy water always causes a gap in the reef.
Good harbours, like that of Mombasa in East Africa, may be
formed in this way.
A theory proposed by Darwin and supported by Dana and
other geologists accounts for atolls as being built up stage by
stage round islands on a sinking sea bottom, a fringing reef
changing to a barrier reef separated by a channel from the
island, and the island itself finally disappearing, leaving only
the ring of upgrowing coral reef with its wave-built islets
covered with palm trees.
This theory is certainly correct for the island of Funafuti,
north of Fiji, where borings show reef materials to a depth
of 1114 feet, and is probably true of many other atolls. In
other cases, however, there is no evidence of the supposed
sinking of the sea bottom, and another explanation must be
looked for. The greatest coral reef in the world extends as a
wide barrier for noo miles along the north-east coast of
Australia, affording a well-protected channel for shipping for
the whole distance.
Shell Fish. The different orders of shell fish, aided by sea
urchins, starfish, etc., probably do even more work in removing
the lime from sea water to form their shells than the polyps
DYNAMIC GEOLOGY in
do in the building of coral, but their work is scattered on all
sea shores, even in the Arctic zone, and is nowhere heaped up
monumentally like a coral reef. Many of our Palaeozoic lime-
stones are made up almost wholly of their shells, and they
have been great rock formers from the Cambrian to the
present. Marl, deposited mainly by shell fish in our lakes, is
of importance in the making of Portland cement.
Vertebrates. There are a few operations carried on by
vertebrates which have a geological bearing, although the
FIG. 44. TERTIARY LIMESTONE WITH SHELLS
results are trifling as compared with those of the foraminifers,
corals, and shell fish.
Seabirds, for instance, form thick deposits of guano on
islands off desert coasts, as near Chile and Peru. Though
these are removed by man as a most useful manure, the clouds
of seabirds gradually replenish the supply.
Among mammals the beaver and man perform engineering
work influencing geological processes. The beaver's dams
form lakes in which the forest perishes, peat and silt are
deposited and ultimately a "beaver meadow" is created.
Man is far the most active geological agent among mammals,
as a farmer clearing and cultivating the land, as a builder of
cities whose crumbling bricks may form the only hills in a
H2 ELEMENTARY GEOLOGY
flat plain like that of Mesopotamia, and as an engineer build-
ing dams and embankments, excavating canals, mining the
sulphides hidden in the earth and roasting them, thus destroy-
ing vegetation and exposing bare hills and plains to rain
erosion. The mining and burning of coal, restoring to the air
carbon dioxide removed millions of years ago, may slowly
modify the climates of the world. The activities of man in
shaping the earth to his needs or wishes go beyond the usual
province of geology, however.
CONFLICT OF FORCES IN THE WORLD
From the account of the epigene forces just given it is
evident that their general tendency is destructive, the tearing
or wearing down of all projecting parts of the earth, moun-
tains, plains, continents, and islands, and the deposit of the
materials as sediments beneath the sea. In time even the
lowlands would disappear by solution, and where land once
was there would remain only shoals in a universal sea. The
hydrosphere, now covering nearly three-fourths of the earth's
surface, would then cover the whole and become complete.
This nihilistic work of water and its auxiliaries has been in
progress since the earliest known times. Even in the very
earliest ages (Grenville and Keewatin) waves and rivers
worked effectively, since water-formed sediments were laid
down on a large scale.
Though the work of destruction has been unintermitting
it has never succeeded in conquering the lands and covering
them with the sea. After every lowering they have always
risen again, so that in the main the continental masses seem
to be permanent.
The conservative factors in the world have been the hypo-
gene forces which have constantly been engaged in uplifting
lands and depressing sea bottoms, restoring the inequalities
which the epigene forces strive to abolish. The earthquake
and the volcano, the two most dreaded manifestations of
these subterranean adjustments of the earth's crust, may
destroy a city, a human anthill, from time to time, but the
DYNAMIC GEOLOGY 113
full result of the hypogene forces is eminently constructive
and restorative.
The failure of either side to win a final victory in the great
war of forces has made the earth the wonderful and beautiful
and habitable globe which we know; and the contest, so
vital to the existence of all living beings, is going on all around
us and should arouse our keenest interest.
GEOLOGICAL TIME
In summing up the effects of many of the forces which have
been referred to, the element of time becomes a factor of
great importance, since great results may come from the
slow accumulation of individually trifling contributions, like
particles of dust blown by the wind or the invisible shells of
foraminifers. Geologists then are greatly interested in the
length of time available in accounting for the changes which
have gone on in the world.
There are various ways of computing the length of past
time, some purely geological, others astronomic or physical.
As an example of geological methods one may take the
number of years required to provide the amount of salt in
the sea, supposing that it has all been brought. in by rivers
with their present annual contribution of salt. This works
out to about 90,000,000 of years.
Attempts have been made to sum up the maximum thick-
ness of sediments deposited in different ages of the world,
assuming a definite rate of formation for each variety of
sediment, and results have been reached ranging from
70,000,000 years to more than twice that length of time.
Physical methods of estimating the permissible length of
geological time have been founded on the rate of cooling of
the earth, following the nebular theory; and on the slow-
ing down of the earth's motion by tidal friction caused
by the moon. These and other methods were believed a
few years ago to limit geological time to not more than
10,000,000 or 20,000,000 years, a quite inadequate supply
for the needs of geology.
However, the comparatively recent discovery of radio-
n4 ELEMENTARY GEOLOGY
active substances in the rocks has completely altered the
situation so far as estimates depending on the cooling of the
earth are concerned. From the relations of radioactivity
certain physicists suggest that rocks from the Pre-cambrian of
Quebec are from 222,000,000 to 715,000,000 years old; and
others even extend geological time to 1,310,000,000 years as
regards rocks found in the United States and 1,640,000,000
for Ceylon. The estimates drawn from radioactivity have
so enlarged the time possibilities of the world's past history
that there is ample room for all the operations geologists find
necessary in building and transforming the rocks of which
the crust is composed.
It is worthy of note that in Canadian geology, which
includes the most complete series of ancient rocks known,
geological forces like those of the present were at work in
the earliest ages. Rain and rivers and large bodies of standing
water are implied by the sediments; volcanoes poured out
lava streams or showered ashes as in later times; and lime-
stones and carbon even suggest life.
These first of known rocks are far removed from the
beginning of the world.
CHAPTER IV
STRUCTURAL GEOLOGY
IN the discussion of the dynamics of the world it has been
shown that various forces are at work modifying and shaping
it in different ways. The structures resulting, that is, the
architecture of the world, may now be considered.
FIG. 45. STRATIFICATION OF LORRAINE SHALE AND LIMESTONE, HUMBER
RIVER, TORONTO
Most of the land surface consists of sedimentary rocks laid
down by water in beds or strata, and it is natural to begin
with the most widely spread structures, those of stratified
rocks. Afterwards the structures of eruptive or igneous
rocks will be considered, and finally those of schistose
rocks which may include modified examples of either of the
two other types.
STRATA
Water and, to a less extent, wind lay down materials bed
by bed, each bed, or stratum, being the result of a more or
"5
n6
ELEMENTARY GEOLOGY
less continuous process. Some break or change in the con-
ditions causes a parting of one stratum from another.
The thickness of a stratum may
vary from an inch or two or even
less in fine materials to several
feet in coarse deposits such as con-
glomerate. There may be less
marked divisions within a stratum
giving rise to lamination.
Where the materials have been
FIG. 46. CROSS BEDDING IN
SANDSTONE, DUE TO WAVES dumped intermittently by wave or
AND CURRENTS, THOUSAND current action over the edge of a
ISLANDS, O
current bedding, with subordinate structures diagonal to the
main stratification. This is often seen in sandstones and
conglomerates. All strata thin out and end somewhere,
but their area varies greatly. Where the sediments come
from a central point, like the mouth of a river, the strata
tend to have an imperfect lenticular form. The surface
of a stratum may show ripple marks due to wind or gentle
waves or tides, and there may also be rain prints and mud
cracks, the latter due to shrinkage on drying. Rarely there
may be tracks or footprints of animals. All of these markings
STRUCTURAL GEOLOGY
117
have their bearing on the history of the beds, since they are
contemporary records of events.
JOINTS
In almost all cases strata are broken asunder by joints
or partings about at right angles to the stratification, and
commonly there are two sets of joints cutting one another
nearly at right angles. In quarrying the dimensions of the
blocks which can be obtained are determined by the thickness
FIG. 48. JOINTS IN LIMESTONE, NAPANEE, ONTARIO
of the stratum and the spacing of the joints. Frequently
the direction of the jointage is uniform for long distances,
implying a common cause.
Joints may not become apparent in a rock till it is quarried,
but in limestones exposed to the weather they may be opened
up by solution, forming fissures several inches wide. It is
important for the quarryman and the miner to understand
the jointage of the stone he is working in, so as to economise
labour and explosives and to obtain well-shaped blocks.
The cause of joints is not very well understood, but it is
generally looked for in the sudden adjustment of rocks under
strain, often accompanied or caused by an earthquake shock.
A torsional or twisting strain may be relieved by two sets
n8
ELEMENTARY GEOLOGY
of fractures roughtly at right angles to one another, which
would account for a common arrangement of joints, and very
probably took place in many cases.
^tf9B^ ^ i
CONCRETIONS
Various chemical changes may go on in a rock long after it
has become a part of a series of beds, through the action of
seeping waters, causing
concretions of different
materials. The commonest
concretions are those of
lime in clay or shale,
rounded or flattened forms
of limestone sharply
bounded and remaining
after the enclosing rock
has crumbled away. When
broken there may be a
FIG. 49. CONCRETIONS OF CARBONATE *Q8SU as a nucleus, such
OF LIME FROM PLEISTOCENE CLAY, as a fern leaf in coal-
measure shales or a small
fish or shell as in the marine clays at Ottawa.
The "kettles" of Kettle Point on Lake Huron are large
spherical concretions of radiating calcite crystals, which have
bent the shale beds apart in their growth, while most lime
concretions do not interfere with the bedding.
Concretions of impure siderite (clay ironstone) are of the
same kind, and in the coal measures of some countries have
been used as iron ores under the names of sphaerosiderite or
pisolitic ores.
Marcasite (a sulphide of iron) is common as concretions in
shales or slate and often occurs in coal.
Flint or chert nodules are really concretions of silica in
chalk or limestone.
In sandstones the concretions show little difference chemi-
cally from the rest of the rock except for rudely spherical
arrangements of limonite. Some of them in the Potsdam
sandstone of eastern Ontario are cylindrical, several feet in
length, cutting across a number of strata, and even ten feet
STRUCTURAL GEOLOGY 119
in width. They separate easily from the rock like tree trunks,
for which they have been taken. The cause of these forms
is uncertain and it may be that they should not be included
with ordinary concretions.
The evidence that in some cases strata have been pushed
aside in the growth of concretions shows that powerful forces
have been at work in their formation, chiefly perhaps the
molecular forces that build up crystals.
ATTITUDE OF STRATIFIED ROCKS
Most sediments have been laid down on a flat or only
gently inclined sea bottom, but in many regions the stratified
rocks are no longer
in their original
position, but are
found more or less
tilted. The amount
of tilt as mea-
, - ,, FIG. 5O. DIAGRAM SHOWING STRIKE AND DIP
sured from the
horizontal is called the dip, which may be expressed in degrees
from o° to 90°. The direction of the dip, i.e. of the greatest
inclination, should be noted also; and a direction at right
angles to it is called the strike, corresponding generally to the
line of outcrop. At o° dip the strike is indeterminable, and
at 90° the strike is the most salient feature. The dip is not
reckoned beyond 90°, though the beds may really have re-
volved through more than a right angle and may actually
be overturned. Instruments called clinometers are used to
determine dips.
The importance of dip in mining operations is evident. If
a coal seam dips uniformly at 20° westwards, one can reckon
the depth to which a shaft would have to be sunk in order to
reach the coal at a point one mile, for instance, west of the
outcrop. However, it should be noted that the dip commonly
changes from point to point and cannot be assumed to be
uniform for long distances.
FOLDS. In most cases the beds are found to be bent, instead
of being tipped as a block on a gigantic scale ; and if the curves
are followed out one recognises a wavelike arrangement, with
120
ELEMENTARY GEOLOGY
a crest or saddle, which is called an anticline ; and a trough,
called a syncline. Occasionally in mountains one can actually
see the beds folded into
anticlines and synclines,
but more often only a
part of the fold is visible.
Anticlinal ridges and syn-
clinal troughs do not
run indefinitely in either
direction, but tend to
FIG. 51. OPEN SYMMETRICAL FOLD SHOW- diminish and at length
ING AN ANTICLINE OR UPWARD BEND disappear when followed
AND A SYNCLINE OR DOWNWARD BEND . ,.
out. Most anticlines are
elongated domes and most synclines elongated basins. The
amount of bending may be slight, giving open folds, or
extreme, when the sides may be forced together, causing a
closed fold.
Folds may be symmetrical, when a vertical plane would
divide the anticline or syncline into similar halves, but usually
FIG. 52. PART OF FOLDING MOUNTAIN, ATHABASCA GAP,
ROCKY MOUNTAINS, SHOWING A COMPLEX SYNCLINE
they are unsymmetrical, and not infrequently they are over-
turned or recumbent. Folds may be "carinate" when a
keel-like anticline or syncline passes upwards or downwards
into unfolded beds.
Folds of various kinds are displayed on a large scale in
the Rocky mountains, running parallel to the direction
of the range and apparently caused by a powerful thrust
from the Pacific. The folded beds may be 20,000 feet or
more in thickness.
On the other hand, in parts of the Selkirks and in the older
STRUCTURAL GEOLOGY
121
•^Milt 'ot)l|>-- '/ "— t
rocks of the east there may be intricate crumplings of the
strata, like wavelets and ripples on ocean waves.
Gentle anticlinal folds or domes are the most favourable
localities to search
for oil, and syn-
clinal basins are
commonly found in
coal regions.
Where rocks are i^,
bent on a very long
and broad scale, FIG 53 OVERTURNED FOLD, CLEARWATER RIVER
often with subordi-
nate undulations as well, the terms geanticline and geosyn-
cline may be used, the latter structure forming the usual
beginning for the building of a new mountain range. A long
and wide depression of the sea bottom becomes more and
more depressed as layers of sediment are piled upon it, until
lateral pressure throws the gentle down-
ward curve of the geosyncline into sharper
folds of the more common type.
In addition to the usual folds con-
FIG. 54-
MO> E
f an antidine and a syncline
there are in some places monoclinal folds with the bend in
only one direction.
ZONES OF DEFORMATION AND OF FRACTURE
Rocks are mostly hard and resistant solids; some of our
building stones, for instance, will stand .a tremendous crushing
strain, and it is a surprise to find that they can be crumpled
into folds like so much cloth or paper. It must not be for-
gotten, however, that all solids yield under sufficient strain,
especially when the process is aided by heat, and act more
or less as if they were plastic. In the case of mountain folds
one must suppose that there was a sufficient load resting
on the beds to force them to yield plastically. We may
assume that at a certain depth all rocks may be deformed
without rupture, and this region below the surface may be
called the zone of plasticity. Above this and reaching to
the surface is the zone of fracture.
122
ELEMENTARY GEOLOGY
Rocks differ greatly in strength, and where strong and
weak rocks are interbedded there will be an intermediate
zone in which some
beds, such as shale,
yield plastically,
and others, such
as quartzite, adjust
themselves by
breaking into
/ blocks. Examples
of this kind are
found in the
Rockies.
FAULTS. In the
upper parts of the earth's crust we shall expect the rocks
to break under sufficient stress, and the blocks thus formed
will slip into a new position of rest. Such adjustments take
place along certain planes of dislocation and are called faults.
Usually the shifting is in a more or less vertical direction and
FIG. 55. FOLDING UNDER THRUST FAULT,
CLEARWATER RIVER
FIG. 56. NORMAL FAULTS, SHOWING A HORST AND A GRABEN
the amount of change of level on one side as compared with
the other is called the throw. There are, however, faults in
every direction, even horizontal, as was proved in the earth-
quake at San Francisco.
Normal Faults. In most examples of faulting one finds
STRUCTURAL GEOLOGY
123
that there has been expansion of the surface, with a tendency
of the blocks to slip down under the action of gravity, the
part with the smallest support
slipping farthest. This is the
natural arrangement and is called
normal faulting. The surface
along which the yielding took
place is called the fault plane,
though it is not always a real
plane; and it is often polished
or even striated, when it is said
to be slicken-sided. Usually clay
or talc or some other secondary
mineral has been formed in a
case of slickensides.
The throw of faults may be of
all dimensions, from a fraction of
an inch to thousands of feet,
and the amount of throw may
diminish in each direction till
the fault runs out; or a single
fault may divide up into man}?-
smaller faults.
Sometimes a solid, broad-based block of rock stands up
centrally, while slice after slice slips down on each side, giving
rise to a horst; and at others the central strip is too poorly
supported and drops, making a long rift or trough, often
called a graben. This is sometimes the case where the central
part of a gentle anticline yields and sinks, the keystone
dropping out of the arch. The basins of Lake Tanganyika
and other lakes in Africa are explained in this way, and the
basin of the Dead Sea is another example.
Reversed or Thrust Faults. Faults may be caused also
by a push which results in an upward movement of the rocks
instead of the normal downward slip, and the term reversed
or thrust fault is applied to them. In this case there is
compression of the surface instead of expansion, and the
type is most frequent and important in mountain regions,
such as the Rockies.
In some cases it seems as if long slabs or blocks of the crust
FIG. 57. NORMAL FAULT NEAR
NIPIGON, ONTARIO
124
ELEMENTARY GEOLOGY
were broken apart longitudinally, and then more or less tilted
and thrust one upon another like ice cakes in a spring flood,
each riding upon the lower edge of the next one. This is well
Castle M C. Li m&ston e Cretaceous Beds
FIG. 58. THRUST FAULT NEAR GHOST RIVER, BOW PASS
Showing Castle Mountain limestone (Cambrian) pushed seven miles over Cretaceous
beds. After McConnell, Geological Suri'ey, Canada.
shown in the eastern part of the Rockies at Bow Pass, where
five blocks may be seen in succession, each with a steep cliff
showing the edges of the strata to the north-east and a gentler
slope following the dip of the strata toward the south-west.
In the case of the outer block the movement has been up a
FIG. 59.
t'noto. by E. S. Moore
MODERN FAULT CONNECTED WITH AN ALASKAN EARTHQUAKE
somewhat inclined plane for a distance estimated at seven
miles. In the highlands of Scotland the Moine thrust fault
has driven Pre-cambrian beds ten miles over Palaeozoic rocks,
and even greater thrusts have been described in Sweden
and in the Alps.
STRUCTURAL GEOLOGY
125
There is some reason to think'that these thrust faults began
as overturned folds, which 'were torn asunder at the sharply
bent crest of the anticline, , thus connecting one type of fault
with folds. There are examples also of regions which have
first been folded and then broken up and rearranged by
faulting, giving very complicated structures.
FIG. 60. DISCORDANCES
DISCORDANCES
Where sediments are formed continuously, each bed resting
regularly and uniformly upon the one below, the strata are
said to be conformable', but there
are many examples known of un-
conformity or discordance in strati-
fied rocks, where the lower and
older beds have been tilted or
folded and then planed down by
the epigene forces before the later , Js
beds were deposited. This gives
rise to a discordance and indicates
an important break in time. The
angular difference between the
two series of rocks may be of all
grades. The beds of the Lower
Palaeozoic atGananoque (Thousand
Islands) rest flatly upon the almost vertical and greatly dis-
torted Pre-cambrian gneisses and quartzites, the oldest rocks
known, and the discordance is one of the greatest imaginable.
On the other hand, there may in some cases be no angular
. _rT discordance separating beds of
very different ages, though the
older beds may have been eroded
into a very uneven surface before
the later ones were deposited.
This relation may be called dis-
The older rocks were eroded but not f ., ,. ,. • -L •. r
tilted before the later strata were Conformity to distinguish it from
unconformity.
There are cases where the older beds had been thrown
into folds and then the surface levelled before the next
rocks were formed, so that the later beds sometimes cut
e or unconformity
in stratified rocks, (b) Pronounced
dscordance between Pre-cambrian
and Cambrian rocks, near Ganan-
oque, Ontario.
FIG. 6l. DISCONFORMITY
126 ELEMENTARY GEOLOGY
them at an angle and at others, over anticlines and syn-
clines, are parallel with them.
Photo, by W. F. Ferrier
FIG. 62. UNCONFORMITY, UTAH
STRUCTURE OF ERUPTIVE ROCKS
SUPERFICIAL OR VOLCANIC STRUCTURES
The work of volcanoes is open to study on the surface and
the resulting structures are well known. Where lava is given
Photo, by Tempest A nderson
FIG. 63. PA-HOE-HOE LAVA, KILAUEA, HAWAII
off from a volcano it forms streams which may spread as
wide, flat, thin sheets if the lava is very fluid, or may be short,
STRUCTURAL GEOLOGY
127
thick, and steeply inclined if it is viscid ; and all intermediate
forms may be found. The thin sheets, if one follows another
somewhat regularly, may imitate the arrangement of sedi-
mentary rocks.
Lava sheets or streams usually have peculiar surface
features; they may have a fairly smooth but wrinkled or
ropy surface, called the pa-hoe-hoe surface in Hawaii ; or a
rough slaggy surface, sometimes extremely rugged, full of
projecting points and edges, called aa in Hawaii. The internal
structure also may be of interest. If a lava stream is somewhat
FIG. 64. A A LAVA, ETNA
fluid in the beginning, steam bubbles may ascend toward the
top, where cooling may have advanced too far to let them
escape. Thus the upper part of the stream may become
vesicular and crowded with small holes. If these holes are
very numerous and slender, the light material called pumice
may result.
AMYGDALOIDS. Ancient vesicular lava usually has the
openings filled with later minerals, such as calcite, agate,
and zeolites, and is then called an amygdaloid, the separate
inclusions receiving the name amygdules, from the Latin
word for an almond. Good examples occur in Keweenawan
lavas near Lake Superior.
128
ELEMENTARY GEOLOGY
PILLOW OR ELLIPSOIDAL STRUCTURE. Where lava flows
into water its surface is very rapidly cooled and lobe after
lobe pushes forward to be
quickly arrested, resulting
in oval masses piled on
one another like sacks of
wool or pillows. This
structure is found in lavas
belonging to our most an-
cient rocks, the Keewatin.
STRUCTURES CAUSED BY
EXPLOSIVE ERUPTIONS.
Where explosions take
place the lava may be
blown into very fine dust,
into somewhat coarser
particles called volcanic
ash, larger ones called
lapilli, and still larger
ones, a few inches or even
several feet in diameter,
called bombs. Such bombs may have rotated in the air and
have been twisted into a spindle shape, or may have cooled
on the surface while gases were still expanding within, the
outer crust being fractured, giving the bread-crust structure.
The loose materials may fall on the land or into water,
forming tuffs of various kinds, sometimes well stratified.
Since more fragments fall near the crater of a volcano than
farther away, the centre grows faster than the edges and a
beautiful conical shape may result, as in Fujiyama or Teneriffe;
and they may be called stmto-volcanoes because of this
arrangement of the loose materials. In most volcanoes there
are both lava streams and fragmental beds, giving a less
regular form, and often accidents in the way of explosions
may destroy the symmetry. In old volcanoes like Etna
eruptions are apt to break out in different places, building
parasitic cones here and there on the flanks of the original
cone. Such small craters formed wholly of loose materials at
a single eruption are often very regularly shaped, and are
called cinder cones. Occasionally a lava stream has pushed
FIG. 65. PILLOW AND AMYGDALOIDAL
STRUCTURE, SUDBURY, ONTARIO
STRUCTURAL GEOLOGY 129
out on one side, destroying the symmetry. Cinder cones are
well displayed in Mexico (see Fig. 15).
UNDERGROUND STRUCTURES
DIKES. Molten rock originates, so far as known, at great
depths, and much the larger part never escapes in volcanoes,
but cools below the surface under very different conditions.
The commonest form in which eruptives occur is in dikes,
which are sheets of rock filling fissures, perhaps opened as the
magma, or fluid rock, ascended. Dikes are apt to be nearly
DIABASE DIKES, SAGLEK, LABRADOR
vertical, though they may change their direction and pinch out
or split up into smaller dikes. Their thickness may be no more
than a fraction of an inch or may reach two hundred vards,
and some dikes of diabase extend for fifty miles or more. Thev
are found, often in great numbers, in all the mining regions of
northern Ontario, and are in some cases supposed to have
brought with them the materials of which the ores were
formed. Their walls are very distinct, except in the case of
pegmatite dikes, which represent the last part of a granitic
magma to remain fluid, and ramify quite irregularly into
the adjoining rocks, which were probably still hot when they
were injected.
SHEET-LIKE FORMS AND LACCOLITHS. Occasionally dikes
i
i3o ELEMENTARY GEOLOGY
can be followed up to a certain level, where they spread out
thinly between two beds of sedimentary rocks, forming sheets
or sills, as may be seen on Thunder bay, Lake Superior. In
most respects they are like horizontal dikes and need no
particular description. The rock must have been very fluid
to permit of this; another structure results if the magma is
more viscid. Instead of spreading widely the molten material
heaps up at a particular level and rises into a cake-like form,
called a laccolith (stone cistern), lifting up the beds above into
a dome. Well-formed laccoliths have a flat floor and dome-
shaped upper surface, but they are often very irregular, and
FIG. 67. IDEAL CROSS SECTION OF A LACCOLITH WITH SHEETS AND DIKES
After G. K. Gilbert.
there are intermediate stages between laccoliths and sills,
called laccolithic sills.
A related structure may take on the shape of a basin, the
floor beneath collapsing as the magma ascends from under it,
as may be seen in the eruptive sheet which brought with it
the Sudbury nickel ores. The sheet in this case was a mile
and a half thick and cooled very slowly under 9000 feet of
sediments, allowing the magma to split up by the aid of
gravity into a lighter rock above (micropegmatite, a kind
of granodiorite) and a heavier rock beneath (norite), while
the heaviest ingredient of all, the sulphides, settled into the
hollows at the bottom.
BATHOLITHS. Laccoliths are known to rest upon a floor of
older rock, but a somewhat similar, though usually larger
STRUCTURAL GEOLOGY
131
structure, called a btitholith (rock of the depths), seems to
reach down indefinitely, its foundations never having been
seen, perhaps because erosion has not gone deep enough to
disclose them or perhaps because the materials join on to a
layer of similar plastic rock below. Batholiths dome up the
Section along A-B
From Northwest to Southeast
— SUDBURY NICKEL DISTRICT —
Scale of Miles
FIG. 68. THE SUDBURY BASIN, ONTARIO
rocks above and probably make the deep-seated sub-structure
of great mountain chains.
The dome formed by a batholith may be low with rocks
above dipping at small angles away from it, or lofty with the
neighbouring rock dipping steeply or even standing vertical.
In this case the whole upper part of the structure has often
been removed by erosion, disclosing the central parts, usually
consisting of coarse-grained granite, granodiorite or diorite.
132
ELEMENTARY GEOLOGY
Within the flatter domes one often finds remnants of the
overlying rocks, "roof pendants" more or less metamorphosed
by the magma into which
they sank.
The magma of batholiths
does not appear to have
been very fluid, but from it
or from some related source
dikes of granite or porphyry
generally penetrate the en-
closing rocks, which must
have been distended and
probably fissured by the
upwelling of the magma
forming the batholith.
Batholiths are the most
characteristic structural
FIG. 69. PLAN AND CROSS SECTION form of our Canadian Lau-
rentian, covering in all hun-
dreds of thousands or a million square miles of northern
Canada with their oval curves, and they make the greater
part of the Coast Range of British Columbia.
STOCKS OR BOSSES. Smaller, but still important, masses of
eruptive magma seem to have ascended into the overlying
rocks without lifting them as domes, perhaps melting their
way through and absorbing more or less of the materials
encountered. These masses of granite, etc., often resist
weathering and stand out as hills when the enclosing rocks
have been removed. Stocks may really be the lower parts of
volcanic necks in some cases.
Some writers speak of plugs of magma driven up through
the strata above as bysmaliths ; and the term chonolith has been
suggested for irregularly shaped masses of intruded rock.
JOINTS OF ERUPTIVE ROCKS
COLUMNS. Practically all rocks, sedimentary or eruptive,
are parted by joints, but apparently for different reasons, the
joints of eruptives being probably due to contraction on
STRUCTURAL GEOLOGY
133
cooling and not to the relief of strains caused by torsion
or folding. Fine-grained eruptives, especially the basalts,
often have a wonderfully perfect system of contraction
joints suggesting the name basaltic columns. These columns
are about at right angles to the surface of cooling and
therefore radiate outwards in volcanic necks, and lie cross-
wise in dikes and stand vertically in sheets of lava or
laccolithic sills.
The columns may be hexagonal in shape, but often have
Photo, by E. M. Burwash
FIG. 70. BASALTIC COLUMNS NEAR MOUNT GARIBALDI, B.C.
five, four, or even three sides, or else may have seven or eight.
The thickness varies from a few inches to several feet. They
are generally broken into segments by a kind of ball and
socket joint, and in a dike they may look like a pile of cord-
wood. Examples may be seen in the diabase dikes and sheets
north of Lake Superior, but more perfect prismatic structure
is displayed by some of the western lavas. The columns of
the Giant's Causeway in Ireland and of the Cave of Staffa
in Scotland are famous.
JOINTS OF COARSER-GRAINED ERUPTIVES. The coarser-
grained eruptives, such as granite, diorite, etc., show much
134
ELEMENTARY GEOLOGY
less regularity of form and give rise to ruder shapes. In most
cases there are joints in three planes, but not always at right
angles to one another. In
many granites one of the
planes is about parallel to
the original surface of the
cooling mass, giving the
effect of banks a few feet
in thickness ; while the other
joints are at right-angles to
this direction. The joint
fissures may allow water to
enter and the angles of
the oblong blocks become
rounded by weathering, re-
sulting in wool sack -like
masses which lie separate
from one another and almost
suggest drift boulders. This
FIG. 7I. SHEETING AND JOINTING IN fe best seen jn UnglaCiated
GRANITE, FOX ISLAND, B.C.
countries, and is well shown
in the Matopos Hills in South Africa'and in central India.
STRUCTURES OF SCHISTOSE ROCKS
FOLIATION
Both sedimentary and eruptive rocks may take on the
schistose structure, which means literally a cleavable struc-
ture, since these rocks can be cleft or split more readily in one
direction than in others. This direction of easy division is
generally due to the arrangement of certain minerals, espe-
cially mica, chlorite, and hornblende, which have their crystals
so arranged that the cleavage planes are parallel. Since
the very perfect cleavage of the micas and chlorite comes
from the thin plates or leaves into which they readily split,
the name foliation may be given to this arrangement of the
schistose rocks.
In the case of gneiss there may be also a banding of different
minerals, some layers having more of the light minerals an4
STRUCTURAL GEOLOGY 135
others of the dark ones, a very characteristic feature of many
Laurentian gneisses. This may be caused by the rolling out of
masses of granite penetrated by basic dikes, or by the penetra-
tion of thin sheets of granite between the layers of schist, by
what is called lit-par-lit injection.
Where a porphyritic rock has been sheared and rolled out,
the porphyritic crystals, especially feldspars, often resist the
pressure better than the other minerals and form augen or
"eyes," with an unbroken central part and crushed materials
tailing out in each direction, the whole forming a bulge in the
foliation of the micas above and below.
The schistose structure of some gneisses is the result of a
dragging of the minerals into parallelism with the edges of
batholiths, as the central, hotter part of the magma con-
tinued to push up after the sides had grown cold. On this
account one finds rather perfect gneissoid or schistose struc-
ture near the margin of batholiths, passing gradually through
the form " granitoid gneiss " to granite proper where no parallel
arrangement of the minerals can be seen.
Gneissoid and other schistose structures are the prevalent
features of the Pre-cambrian of northern Canada, and are
usually steeply inclined or nearly vertical, as if the whole series
of rocks was on edge. Many of the physiographic features of the
region, ridges, ravines, river channels, etc., are bound up with
the schistose arrangement of the rock-forming minerals, which
has resulted from ancient mountain-building operations.
SLATY CLEAVAGE
A structural feature confined to fine-grained argillaceous
rocks, called slaty cleavage, is wide-spread and important in
many places. It resembles lamination in unchanged sediments,
but has no real relation to sedimentary layers and may cut
across the lamination at any angle. Slaty cleavage causes a
parting into thin plates or sheets, and is not unlike the more
perfect varieties of schistose structure in this respect. It is
not the result of the cleavage of micas, however, but is caused
by the rearrangement of the small particles of shales by
shearing motions under great pressure, the particles swinging
so that their longest axes are parallel.
136 ELEMENTARY GEOLOGY
Slaty cleavage may be very persistent in dip and direction
over miles of mountain range, as in the Selkirks, and is
evidently the result of wide-reaching causes connected with
mountain building.
The practical value of this power of splitting into thin
uniform plates is shown in the preparing of slates for
roofing purposes.
PART II
HISTORICAL GEOLOGY
CHAPTER I
THE MAKING OF THE WORLD
ONE is apt to think of the world as a finished work like a
statue, hewn and polished long ages ago by some great artist
and left complete and changeless. We speak of the "everlast-
ing hills" and of "terra firma" as if the present state of things
were permanent; and yet we are everywhere surrounded by
proofs that the world is not finished, but is constantly under-
going change. The summer rain makes gullies in the fields
and carries down mud to the streams; the melting snow in
spring turns all the streams to torrents that hurry down mud
and sand and gravel and even large stones to the lake or sea ;
and the frost quarries blocks of the hardest rock from the
cliffs, heaping a talus at their feet. If one follows up the work
of wind and weather and running water, it soon becomes
evident that not alone the hills but all the land that rises
above the sea is being constantly attacked and the materials
dumped on the sea bottom. If nothing interfered with the
process, in time every continent and island would be carved
down to sea level, and finally a universal ocean would cover
all the world.
This catastrophe has never taken place, however, because
there are counteracting forces that lift up the sea bottom in
places to make dry land, as one can see on the old marine
beaches still containing sea shells hundreds of feet above
the Gulf of St. Lawrence in eastern Ontario and Quebec. In
many places one even finds ancient sea shells in the rocks of
mountain tops.
It is evident that while some forces are tearing down the
mountains and devouring the dry land, others are heaving up
the surface and rebuilding the hills and mountains; so that
137
138 ELEMENTARY GEOLOGY
the earth has never been finished, but is still in the making.
The earth was not created once for all ages ago and left as
finished, but creation is still going on all about us.
Nevertheless, these processes cannot be eternal ; they must
have had a beginning, and one naturally asks where the
materials came from and how they were brought together to
form the earth as we know it. In regard to this certain facts
are known, and two very interesting theories have been
proposed to account for them.
The crust of the earth with its covering of water and air is
made up of a large number of chemical elements, and it has
been shown by the spectroscope that most of these occur in
the sun as well as in the more distant stars. Beside this, the
cold solid bodies that come to the earth from space, the
meteorites, contain no new elements. They are composed of
familiar substances found in the earth, though in different
proportions from those of terrestrial minerals. If the rest of
the visible universe consists of the same ingredients as our
earth, though in the gaseous form owing to heat, and if the
dark solid bodies of space also, so far as they reach us, contain
only well-known elements of the earth, it is highly probable,
if not certain, that the earth has had an origin similar to that
of the other bodies in the universe.
It has just been mentioned that bodies made up of intensely
hot incandescent gases and also cold and dark bodies exist in
space, both composed of the elements found in the earth.
One could imagine the earth as beginning either as a mass
of hot gas or as a swarm of cold, solid particles compacted
together; and both theories have been advocated, the first
under the name of the Nebular Theory, and the other as the
Planetesimal Theory. An outline of these two hypotheses will
be given.
THE NEBULAR THEORY
This theory was first suggested by the philosopher Kant,
but was worked out more completely by the astronomer
Laplace, and was so simple and beautiful that for many years
it was generally accepted as true. Our solar system is supposed
to have begun as a vast lens or disc of hot gases containing all
THE MAKING OF THE WORLD 139
the material of the sun and planets and extending beyond the
orbit of the outermost planet. This lens of gas, or nebula,
was supposed to be in rotation about a central axis and to be
cooling down by the loss of heat into space. As the cooling
progressed the lens shrank correspondingly, but the rate of
motion remained the same, so that the speed of rotation of
the outer parts of the nebula, travelling round a smaller circle,
steadily increased. In time the centrifugal force of this outer
belt of gas just balanced the gravitational pull of the rest of
the nebula and a ring of gas was left behind. This is called
annulation. Later the material of the ring came together
about a centre and rotated about its own axis in the same
direction as the parent nebula.
Ring after ring was left behind at definite intervals, and
some of the subordinate masses of gas repeated the process
on a small scale. The primary spheres of gas condensed to
form planets and the secondary ones made satellites like our
moon. The vast, central, remaining mass of gas, still incan-
descent, is the sun; and the sun, the planets, and the satellites
with few exceptions rotate in the same direction; while the
planets have orbits nearly in the same plane, which is also
nearly the plane of the sun's equator. The whole system is
steadily cooling ; all the inner planets, like our earth, are cold
and solid at the surface ; the larger outer planets may still be
quite hot ; while the huge central mass, the sun, still remains
intensely hot.
Following the regular course of the hypothesis, our earth
began as a sphere of glowing gas extending beyond the orbit
of the moon, which was formed from a ring of gas left behind
during cooling and contraction. Later the earth became a
molten ball with an immense atmosphere, including the present
gases and other volatile constituents, such as water and carbon
dioxide. The white-hot, molten sphere cooled so far that a
solid crust of rock formed, and this at length lost its red heat
and reached a temperature where liquid water could exist,
collecting in the hollows to form the sea, though still too hot
to permit of life. Finally the surface of the earth and the sea
upon it became cold, ordinary geological conditions com-
menced, and lowly plants, and later animals, were introduced,
spreading far and wide in the waters,
140 ELEMENTARY GEOLOGY
While the broad outline of the hypothesis seems beautifully
simple and attractive and accounts for some well-known
phenomena, such as the rise in temperature in depth as
shown in mines and bore holes, and the shape of the earth
that of a rotating sphere of liquid, yet a careful study brings
to light a great number of discrepancies between the theoty
and the facts of astronomy and geology. Scarcely any of the
astronomical features of the solar system agree exactly with
the requirements of this hypothesis; the planets do not
revolve about the sun exactly in the plane of the ecliptic,
as they should, and their axes of rotation are all inclined
to it instead of being vertical as one would expect. Some
of the satellites revolve in the wrong direction and with an
unaccountable speed. A careful mustering of the known
nebulae shows that the annular form is very rare, while
many of them have spiral shapes: this does not accord
with the requirements of the nebular hypothesis as origin-
ally stated. For these and other reasons astronomers find
the theory unsatisfactory.
Geologists also have numerous and serious objections to it.
If the nebular plan was carried out with anything like exact-
ness, the earth should be a perfect spheroid of rotation with
no elevations, such as continents and islands, nor great
depressions, such as ocean basins; and the sea should cover
the earth's crust everywhere to the same depth, forming a
complete hydrosphere, just as there is a complete atmosphere.
Again, the oldest known rocks all over the world are sedi-
mentary, i.e. they were formed under water; and nowhere
do we find any remains of the earth's supposed crust formed
by the cooling of the molten sphere. At the very beginning
of known geological time there were bodies of water, so that
the earth could not have been hot enough to evaporate
the seas. Proofs of an ice age at a very early time in the
earth's history show that for many millions of years the
earth has not been steadily cooling down as the nebular
hypothesis demands. Instead of this we know that con-
ditions as to temperature have fluctuated up and down at
various times, the changes keeping within such narrow
limits that living beings have inhabited sea and land for
an immense period of time.
THE MAKING OF THE WORLD 141
THE PLANETESIMAL THEORY
The fall of meteorites proves that there are cold and solid
materials for world building still available in space, and a
"meteoric" theory of the origin of the earth was proposed
many years ago, according to which a swarm of meteorites
moving swiftly and generating heat by their collisions might
ultimately combine to produce a molten globe as the start-
ing point for our earth; but this theory has not received
much support.
More recently the Planetesimal Theory has been brought
forward by Chamberlin, a well-known geologist, and Moulton,
an astronomer, to account for the creation of the earth. The
word " planetesimal " means a minute planet, a cold particle
travelling through space at planetary speed. In essence the
theory describes the world as built up mainly or wholly by
the coming together of such cold particles under the influence
of gravity. The innumerable "shooting stars" which still
bombard the earth, coming swiftly out of cold space, shining
brightly for a moment from the intense friction with our
atmosphere, and then being dissipated to fall as minute
particles to the earth, may be looked upon as remnants
of the vast numbers of planetesimals which combined to
form the earth.
An elaborate process has been suggested to connect the
formation of planets with the "knots" of light often observed
in spiral nebulae, but it would lead too far into astronomical
speculations to discuss it here. The theory supposes a long
period of growth by the accumulation of the planetesimals,
the surface of the central sphere remaining cold. Until a size
greater than that of the moon was attained, no atmosphere
could be held by such a growing world because of its small
gravitative power; but ultimately the materials of the air
and also of the water of the world would arrive and surround
the central-mass. Increasing compression by gravitation
would take place as the mass grew and heat would result,
with chemical reactions and crystallisation of the compounds
formed. Tidal kneading due to the pull of the moon and sun
would play a part and radioactive matter coming in with
142 ELEMENTARY GEOLOGY
the planetesimals would produce heat ; as a result the interior
of the earth would become hot, parts of it hot enough to melt
as lava and eruptive rock. Yet the surface of the earth would
remain cool enough from the beginning for water to exist in
the liquid form and carry on its characteristic work as shown
in the stratified rocks.
There is much greater flexibility in the planetesimal theory
than in the nebular one, and the suggestion of a world cold
from the beginning, perhaps even warming up through the
ages, fits much better with the demands of historical geology
than the supposition of a molten world slowly cooling through
the whole of geological time.
It should be remembered, however, that the planetesimal
theory is still under discussion. It must not be looked upon
as a proved fact, but rather as the most probable way of
accounting for the earth and its history: it may undergo
modification as knowledge increases.
CHAPTER II
THE GENERAL PRINCIPLES OF HISTORICAL GEOLOGY
HISTORICAL Geology, as the name implies, is simply the
history of the earth from the earliest time of which we have
evidence in the rocks to the dawn of conditions as we now know
them. This history is two-fold; it is at once a record of
physical events and an account of the various races of
organisms which have inhabited the earth. Incidentally
the present position, character, and extent of the component
layers of rock form part of the subject of historical geology.
Theories as to the origin of the globe, however useful they
may be to the geologist, are not commonly regarded as part
of historical geology. We begin with the most ancient actual
evidence and trace the history onward from that time.
History, like time, cannot be other than continuous, but
even human history has many gaps owing to the failure of a
record. In geological history, however, an almost continuous
record must have been made, since land and water, with the
consequent erosion and sedimentation, have always existed.
It by no means follows, however, that we shall ever be able
to read the story continuously, because some of the pages
may still be under the sea, others hidden by overlying strata,
and still others totally destroyed by subsequent erosion. It
is evident also that the rock pages of this history are not piled
one above the other continuously in any one place, but that
the leaves are scattered over the globe, some here and some
there. No country, however large and varied, contains within
its borders the whole series of strata from the beginning to
the present time. It is the business of the geologist to gather
together the scattered pages from the whole world and arrange
them in chronological order, or, in other words, to decipher
the history of the globe.
THE STUDY AND CORRELATION OF STRATA
It is apparent that our knowledge of past events can be
acquired only by a study of the rocks themselves. There is
144 ELEMENTARY GEOLOGY
scarcely any fact revealed in the examination of rocks that
may not assist in increasing our knowledge of geological
history. In order to interpret into history the phenomena
exhibited by rocks it is necessary to understand the processes
now at work on the globe. For instance, we see the waves on
a sandy shore sorting and arranging the grains of sand : when
we find sand grains similarly arranged in an ancient stratum
of rock we may safely infer that it was formed by wave action
near an ancient shore. We see shells being embedded in mud
along a coast: when we find similar shells in layers of hard
rock we may conclude that that rock was formed at or
below sea level, although it may be now thousands of feet
above the sea.
Admitting, therefore, that almost any fact revealed by the
rocks throws light on their history, it has been found, never-
theless, that certain principles are of especial value in piecing
together into a chronological whole the scattered pages of
the earth's history. These are:
SUPERPOSITION. This principle may be briefly stated as
follows: the stratum above is younger than that beneath.
For instance, in ascending the gorge of the Niagara river we
pass upwards from a layer of red shale to a layer of sandstone,
to grey shales and limestones, and finally to a heavy layer of
dolomite. These various layers correspond in age to their
position in the series, the red shales at the bottom being the
oldest and the dolomite at the top the youngest.
UNCONFORMITIES. When layers of rock lie evenly one on
another, as at Niagara, they are said to be conformable, and
one may conclude that the record is fairly complete; but in
many cases the succession is broken by unconformities or
discordances that interrupt the record, as though a leaf or
chapter had been torn out of a book. In such a case one
finds the lower beds more or less upturned and their edges
worn off, while the later rocks rest upon the planed-off surface.
In general, one can interpret an unconformity as meaning
that the earlier rocks had been tilted or folded and thus raised
above the sea, where weather, frost, and running water de-
stroyed the projecting parts; while afterwards the region
was lowered beneath the sea again before the later set of
sediments was deposited. It is evident that these processes
PRINCIPLES OF HISTORICAL GEOLOGY 145
require time for their accomplishment, so that a marked
discordance means a very considerable gap in the record.
Beneath some of our older formations one finds a surface
with structures corresponding to the base of a great mountain
range, and one can infer an astonishing series of changes,
where rocks laid down on a sea bottom have been bent up
into domes or folds thousands of feet high and penetrated by
dikes or masses of molten granite. Then the whole vast chain
has been slowly attacked and carved down by superficial
forces until the surface has been levelled almost to a plain.
Finally the later sheet of sediment has been laid down on the
upturned edges of the ancient -structures. Such a discordance
undoubtedly implies an interval of long ages, probably many
millions of years. What happened during the vast interval is
recorded only negatively by the mountain stumps that remain
outlining the foundations of the huge structures destroyed
by "the tooth of time" while the region stood above the
level of the sea.
Unconformities are generally distinct and easily recognised
when any considerable area is studied; but occasionally
there is no angular break between the two series of rocks, so
that one could imagine them to form a continuous succession.
In such disconformities, as they may be called, the older
rocks have usually been more or less cut by valleys, which
have been filled in by the later sediments.
BASAL CONGLOMERATES. Where an upper series of rocks
begins with coarse materials, forming a "basal conglomerate,"
the break is instantly evident, even if no unconformity of
angle is to be seen between it and the lower series. Such a
conglomerate, made up of fragments of the bed beneath,
proves that the lower series had been consolidated into firm
rock and had then been broken up, the angular fragments
being rounded by currents or waves or even by glacial action
before the materials were worked up into the later formation.
All these requirements mean the lapse of time. If pebbles or
boulders of several kinds of rocks derived from different
sources occur in the basal conglomerate, the destruction of the
older series must have been widespread and the time interval
probably long.
Where two or more unconformable series of rocks have
i46 ELEMENTARY GEOLOGY
been folded, squeezed, and rolled out in mountain building,
the planes of discordance may become unrecognisable and
the separation of the formations may be difficult or impossible.
Basal conglomerates, however, even if the pebbles are rolled
out into lenses, may give much help in disentangling the
relations if their materials are well enough preserved to
determine the beds from which they were derived. Where the
rolling out has gone to the extreme, as in some schistose rocks,
even the pebbles of conglomerate disappear, and there is often
no clue to the order of succession.
LITHOLOGICAL CHARACTERS. Where other more satisfac-
tory means of working out the succession of the rocks are
not available, one may make use of the actual nature of the
rocks themselves. If rocks at different places are alike it is
natural to think of them as formed under the same conditions
and at the same time, and sometimes one can actually
follow a particular rock from point to point with little or no
change, thus proving positively that two widely separated
outcrops are continuous with one another and therefore
of the same age.
There are cases, however, where one can begin with one
rock, such as sandstone, and end, perhaps miles away, with
another rock, such as shale. These two rocks were evidently
formed at the same time and in the same body of water, but
under different conditions, sand being deposited at one place
and mud at another, and a mixture of the two at intermediate
points. This shows that the lithological method of correlating
rocks at a distance from one another must be used with
caution, particularly when one remembers that similar con-
ditions resulting in similar rocks have recurred again and
again in the earth's history.
FOSSILS. Except in the very oldest rocks, the evidences of
the existence of plants and animals are of the highest value
in working out the orderly succession of the strata and in
correlating the rocks of one locality with those of another. In
addition, the history of the organisms which have inhabited
the globe is, in itself, a part of historical geology and goes
hand in hand with the record of physical events to make up
the history of the earth.
We do not know when life began on the earth, and it is
PRINCIPLES OF HISTORICAL GEOLOGY 147
doubtful if we ever shall know. Evidences of the existence of
organised beings have been found in very old rocks, but not
in the most ancient rocks of all. Whether or not animals or
plants inhabited the globe in this very early time, who shall
say? In the science of geology negative statements may
sometimes be made with certainty; generally, however, such
statements are intended to express only our present knowledge
of the point in question. Particularly with regard to the
history of life one must remember that statements as to the
non-existence of certain animals at certain times mean only
that evidences of their existence have not been found.
We know that organised creatures have inhabited the globe
continuously from the time of their first appearance to the
present. We know that life has changed, one group of
organisms being succeeded by another in orderly succession
throughout the geological ages. We know that the older an
organism is the more it differs from creatures now living.
Finally we infer, on very substantial grounds, that these
different races of organisms have not been separately created,
but that the younger has descended from the older by a
process of organic evolution.
The concrete evidences on which the above assertions are
made are known as fossils, and that branch of geological
science which deals with this evidence is paleontology. One
should avoid the popular conception of a fossil as the remains
of an extinct organism, or the equally erroneous idea that a
fossil is something petrified or converted into stone. Anything
found in the rocks that indicates indubitably the existence of
an organism in time earlier than the Recent is a fossil. Among
the more obvious fossils are shells, in the natural condition
or altered into some other substance (petrified), teeth, spines,
scales, bones, wood, spores, seeds, and in rare cases even
flesh and hair. Less obvious, but just as truly fossils, are
moulds and casts of shells or other parts of creatures, impres-
sions of leaves, footprints, borings, burrowings, and excre-
ments. A shell found buried in the sand or mud on the shore
of Lake Ontario is not a fossil; but the same shell found in
the same vicinity but in a stratum of sand or mud not formed
by the present Lake Ontario is a fossil. Fossils, therefore, do
not necessarily represent extinct organisms.
148 ELEMENTARY GEOLOGY
The number of known fossils is enormous; hundreds of
thousands of different creatures have inhabited the globe
throughout the geological ages. The history of these creatures,
their habits, their evolution, their migrations, their battles
for supremacy, their rise and fall constitute a large part of
historical geology.
The time during which a creature is known to have existed
is called its range. Some fossils have a short range and others
a long range. Naturally the long-range forms belong to domi-
nant races represented by great numbers of individuals1
such forms are worthy of especial mention in recounting the
history of their time. Short-range forms are usually repre-
sented by fewer individuals, and they may be confined to a
single formation or even to a single stratum: these are less
worthy of mention in a general account of the life of their
time. On the other hand, they rise to the highest rank of
importance in the eyes of the professional geologist. The
very fact of their short range enables him to regard them as
"thumb marks" of the stratum to which they belong and
renders them of inestimable value in fixing the relative age
of the associated strata.
The rocks of the Niagara gorge, already used as an example,
contain some long-range and some short-range fossils: the
former are interesting in that they indicate the general life of
the time, but the latter are like dates on a coin, fixing the age
of the rock which contains them. If we find an isolated bed
of rock, perhaps miles away, containing the same fossils as
one of the beds at Niagara, we are justified in concluding that
it is of the same age as the corresponding bed there.
Unfortunately many rocks, particularly the older ones,
contain no fossils, so that other methods must be used to
determine their age. Where the succession of the rocks has
been worked out on a physical basis, fossils may be used to
supplement the conclusions arrived at: for instance, the
fossils below and above an unconformity are unlike, and the
greater the unconformity the greater is the difference in the
fossils. In the case of a disconformity, the fossils below and
above the break are usually different, but not extremely so.
A difference in the fossils may lead a geologist to suspect
the existence of a disconformity, and the discovery of a
PRINCIPLES OF HISTORICAL GEOLOGY 149
disconformity will lead to a careful search for fossils as
corroborative evidence.
Even where the succession of the different beds of rock is
continuous one cannot always be sure of their order in time.
Where a fold has been closed and its upper part carved away,
leaving the two sides pressed together and vertical, there are
often puzzling relationships ; and where a succession of strata
has been overturned in mountain building, the lower beds
may be younger than the upper ones. There are even cases
where ancient rocks have been pushed bodily over much
younger rocks, so that the overlying bed may be millions of
years older than the one beneath, as in the thrusting of ranges
of the Rocky mountains over the foothills in southern Alberta.
It is evident then that the correlation of the rocks of different
regions, where the evidence of fossils is wanting, presents many
difficulties ; so that the relations of the ancient crystalline
rocks without fossils can seldom be worked out with as much
certainty as those of later ages. Since more than half of
Canada consists of these ancient rocks, it is evident that we
have one of the most difficult regions to study in this respect ;
but the greatness of the area and the unusually good ex-
posures of the rocks give probably the best opportunity in
the world for working out their relationships.
Even when working on fossiliferous formations one must
remember that the record available is usually that of the sea
bottom only. Marine plants and animals which have hard
parts may be very well preserved, but there may be little
evidence of conditions on the land. The record of the inhabi-
tants of the land, especially in the older periods, is usually
wanting and is always very meagre. A leaf or a piece of wood
waterlogged and buried in the mud, or a few bones or a feather
brought down by some stream, may be all that remains to us
of the plants and animals of a continent.
At the present time rocks are being formed under very
different conditions in different parts of the world. In the
deeper parts of the sea, organisms are being entombed which
do not exist in the shallow waters along the coast; Arctic
organisms are entirely different from those of the Torrid
Zone ; the freshwater shells which accumulate on lake bottoms
differ from the marine shells of the ocean ; swamps and lagoons
150 ELEMENTARY GEOLOGY
are inhabited by creatures not known in the open sea. It is
apparent, therefore, that, at the same time, very different
rocks containing very different organisms are being formed.
These varying sets of conditions are known as fades; thus
we have marine, freshwater, pelagic, littoral, and other facies.
There is no reason to doubt that conditions of sedimentation
varied as greatly in geological time as they do at present,
consequently we may expect to find strata of different facies
throughout the geological record. At once we are confronted
by an added difficulty in deciphering the geological history
of the earth, but as the record left by marine organisms is the
most continuous, we rely on that almost entirely for the sub-
dividing of rocks and time. Strata of facies other than marine
are fitted into the geological column by whatever accessory
evidence is available. »
While marine deposits rank first in importance, there are,
however, some land deposits preserved on a large scale, giving
clear evidence of what took place on the continents; such as
desert formations and glacial "tillites" or ancient boulder
clays. A red, irregularly bedded sandstone may be clearly
the work of desert winds, though now thousands of miles
from the nearest- arid region; and one may find striated
stones in tillites within the tropics on several continents,
proving the former existence of great ice sheets where now
frost is unknown. The growths in low-lying swamps, also,
may be preserved by a sinking of the land allowing marine
deposits to cover them, and sometimes an old soil with the
trunks of trees may be sealed up in the same way.
THE SUBDIVISIONS OF GEOLOGICAL TIME
The preservation of land deposits is very infrequent in the
older rocks and by no means common in the later ones, so
that our time scale depends mainly on the sediments of the
sea. Since the inhabitants of the sea have often left their
shells or other hard parts to be studied by the palaeontologist,
the broad divisions of geological time are usually made in
accordance with the character of the marine life of the
different eras. Thus, in most works on geology, the world's
history is divided into grand subdivisions on the basis of life.
PRINCIPLES OF HISTORICAL GEOLOGY 151
We distinguish the Palceozoic, or time of ancient life, the
Mesozoic, or time of middle life, and the Cenozoic, or time of
recent life ; and some geologists place a Proterozoic before the
Palaeozoic, and even an Archeozoic before that, although we
know very little of the life of the world before the beginning
of the Palaeozoic.
In former times a numerical classification was employed,
the oldest rocks then known being the Primary, the Mesozoic
the Secondary, and the Cenozoic the Tertiary. While the
terms "Primary" and "Secondary" have entirely fallen into
disuse, the term "Tertiary" is still employed for a division of
the Cenozoic. Frequently the whole time before the Palaeo-
zoic is included under the term Archcean, meaning simply
"ancient," but in the latest works the rather clumsy expres-
sion Pre-cambrian is made use of for the time before the first
distinctly fossiliferous formation.
Just as a day is divided into hours, and an hour into
minutes, etc., we require corresponding terms for our sub-
divisions of geological time, but it is evident that the same
terms will not apply both to a division of time and to the
corresponding division of the rocks made during that time.
For instance, we may speak of a subdivision of time as an era,
but we cannot call a division of rocks an era. Much confusion
has arisen in the use of terms for the various subdivisions of
rocks and time. In an attempt to standardise the method of
nomenclature the International Geological Congress proposed
the following system:
TIME TERMS ROCK TERMS
Era Group
Period System
Epoch Series
Age Stage
Substage
Zone
Unfortunately, this system has not been universally adopted,
perhaps because the familiar expression "Formation" is not
included. The system employed by the Geological Survey of
Canada is as follows :
152 ELEMENTARY GEOLOGY
TIME TERMS ROCK TERMS
. Era
Period System
Epoch Series
Stage Formation
Member
In this method of nomenclature the word "Group" is not
used in a definite sense as the rock equivalent of "P>a," but
it is employed to designate an assemblage of strata the exact
subdivisions of which may be unknown or in doubt.
Geological time, therefore, is divided into grand divisions,
eras; the eras into periods; the periods into epochs, etc. In
order to distinguish between the different eras, periods/ and
minor divisions, it is necessary to give a name to each of them.
In coining such names it is now the universal practice to use
only geographical terms; thus, Onondaga stage if speaking
of "time and Onondaga formation if speaking of the rocks. In
the early days of geological science this method was not
employed, and in consequence many terms were introduced
which are not in accord with the geographical method of
nomenclature. As already stated, the greatest divisions of all
are based on life terms, Paleozoic, Mesozoic, etc., and others,
such as Carboniferous, on the character of the rock itself.
Strictly speaking, the name of an era or other division of
either time or rocks is a proper adjective and should be
followed by the noun "era," or whatever term is appropriate.
In practice, however, it is customary to omit the noun and to
write "the Palaeozoic," "the Silurian," without introducing
either the time or rock term.
Geology is a progressive science, with new discoveries con-
stantly being made, and with new points of view constantly
being set up; in consequence, it is not surprising that authors
differ in their method of classifying rocks and time. No two
men in writing a history of human events would divide their
matter similarly into books, chapters, etc. Is it to be expected
that the much more complex history of the earth will impress
all observers in exactly the same way? At the end of this
chapter a table is given which indicates the method of
classification employed in this book.
PRINCIPLES OF HISTORICAL GEOLOGY 153
The age of eruptive rocks may be determined in most cases
by their relationships to sedimentary formations. Lava
streams or beds of volcanic ash lying between two sedimentary
rocks are evidently of intermediate age, and any eruptive
mass that penetrates sedimentary beds is clearly of later age
than those beds. Where eruptive rocks cover large areas to
the exclusion of sediments, and where there have been erup-
tions at different times and of different kinds, the age relations
become more complex ; but often one can work out a succes-
sion of events, one eruptive penetrating an earlier one as
bosses or dikes, thus disclosing the relative age.
Where, however, the region has been acted on by mountain-
building forces and has suffered metamorphic changes, trans-
forming the original massive rocks into schists and gneisses,
the order of succession is much more difficult to unravel. The
great developments of granite and gneiss in northern Canada,
often out of reach of any sedimentary rock to indicate the
time scale, provide very difficult problems to solve, since the
granites and gneisses of one period may be very much like
those of another, as in the case of the so-called Laurentian
and Algoman rocks.
Eruptives are sometimes looked on as accidental features
and are not included in the general time scale founded on the
succession of sedimentary rocks, but where they cover great
areas, as in Canada, the problem of their age and relations to
the sediments cannot be passed over despite the difficulty of
working them out.
In the table on the following page the names printed in
italics are used only in America.
TABLE SHOWING THE MAIN DIVISIONS OF GEOLOGICAL TIME
CENOZOIC ERA
PERIOD
EPOCH
Quaternary
Pleistocene
Tertiary
Pliocene
Miocene
Oligocene
Eocene
Palaeocene
MESOZOIC ERA
Cretaceous
Cretaceous
Comanchian
Upper Cretaceous
Lower Cretaceous
Upper Jurassic
Jurassic Middle Jurassic
Lower Jurassic = Liassic
Triassic
PALEOZOIC ERA
Permian
Carboniferous
Mississippian
Upper Carboniferous
Lower Carboniferous
Devonian
Upper Devonian
Middle Devonian
Lower Devonian
Silurian
Upper Silurian = Cay ugan
Middle Silurian = Niagaran
Lower Silurian — Oswegan
Ordovician
Upper Ordovician — Cincinnatian
Middle Ordovician = Champlainian
Lower Ordovician = Canadian
Cambrian
Upper Cambrian = Croixian
Middle Cambrian = A cadian
Lower Cambrian = Waucobian
L ARCHAEAN OR
PRE-CAMBRIAN
PROTEROZOIC
ERA
Late Proterozoic
Keweenawan
Animikie
Huronian
Early Proterozoic
Algoman
Sudburian or Timiskamian
1 ARCHIE-!
OZOIC
ERA
Laurentian
Keewatin and Grenville
CHAPTER III
THE NOMENCLATURE AND CLASSIFICATION OF
ORGANISMS
THE history of the development of life on the earth is in-
timately connected with the record of physical events. The
study of fossils is a part of geological science necessary for
the historical account and of practical value in working out
the sequence of the rocks.
Fprtunate is the beginner in geology who has a knowledge
of the sciences of zoology and botany, for fossils are closely
related to the animals and plants now inhabiting the earth.
So close is this relationship that the methods of study used in
zoology and botany are equally applicable in the case of fossils.
The organisms of the past are links in one great chain of life,
and they may be fitted into any scheme of classification that
includes all living creatures.
To the practical geologist the ability to recognise a fossil on
sight is of the first importance. He does not require a name in
order to fix the fossil in his memory, but in order to speak or
write of it some short and definite designation is necessary.
Many living creatures have popular names, but fossils, being
little known except to scientists, have not acquired names of
that kind. In consequence the scientific method of nomen-
clature is used almost entirely for fossils.
The individual organism, animal or vegetable, living or
fossil, is known as a species and is given a name ; for instance,
the American elm is called Ulmus americanus: the latter
word " americanus" refers only to this species, but the former
word " Ulmus" is applied to other kinds of elm and is followed
by a second word to indicate the species. In other words, all
the different kinds of elms belong to the genus Ulmus, but
only the American elm is Ulmus americanus. This system
of naming is quite the same as that used for persons, except
that the order of the two names is reversed. John Smith
would become Smith John if written according to the
usage of scientists.
I55
156 ELEMENTARY GEOLOGY
This method of naming indicates also the fundamental
principle underlying the classification of organisms. The
species Ulmus americanus is an individual plant, but all related
forms are included in the genus Ulmus. Similarly, related
genera are grouped together in families, families in orders,
orders in classes, etc. Classification, therefore, serves two
main purposes: it enables us to speak and write of organisms
without the constant use of long explanations, and it in-
dicates the relationships that exist among the various kinds
of creatures.
It is obviously impossible in an elementary work on geology
to attempt anything like an adequate description of the various
kinds of organisms; nevertheless, the student should realise
that a knowledge of organisms is an essential part of geology.
On the other hand, lest the beginner be discouraged, he should
remember that many eminent geologists have only a general
knowledge of fossils: in these days of specialisation they turn
to the palaeontologist for a solution of those problems which
demand an intimate knowledge of fossils.
In this work a short description of the different important
groups of fossils will be given in the historical account, at the
times when they first appear. The following brief synopsis of
the classification of organisms contains only those groups of
creatures of importance in geological history. The student is
advised to make use of this table for reference when he is
reading the accounts of fossils given on later pages.
AN OUTLINE OF THE CLASSIFICATION OF
ORGANISMS
ANIMAL KINGDOM:
Sub-kingdom INVERTEBRATA. Animals without backbone.
Branch PROTOZOA. Animals of one organic cell only.
Order FORAMINIFERA. Small animals with delicate shell of
carbonate of lime.
Branch CCELENTERATA. Animals with a single body cavity for all
vital functions.
Class SPONGI^E. Pores through the wall of the body; skeleton
of spicules of lime, silica, or horny matter.
ANTHOZOA. The corals. Body wall without pores.
HYDROZOA. Resemble corals but are smaller and differ
in some details.
CLASSIFICATION OF ORGANISMS 157
Order GRAPTOLITOIDEA. Extinct order. See page 206.
STROMATOPOROIDEA. Extinct order. See page 224.
Branch ECHINODERMATA. Animals covered with plates of car-
bonate of lime; water vascular
system present.
Class CRINOIDEA. Plated body or cup attached to the sea floor
by a jointed stem; circlet of waving arms
above.
CYSTOIDEA. Resemble crinoids but with less development
of arms. Plates sometimes porous.
Extinct.
BLASTOIDEA. Resemble crinoids but have bud-shaped
bodies and plumes instead of waving
arms. Extinct.
ASTEROIDEA. Free-swimming star fishes; not attached
to sea floor; mouth downward; star-
shaped bodies.
ECHINOIDEA. Free-swimming sea urchins; body spherical
or cake-shaped, cardiform, etc.
Branch VERMES. The worms. Bilateral, elongated animals, seg-
mented or unsegmented.
Class ANNELIDA. The segmented worms. Body composed of a
number of joints. Seaworms, earthworms,
etc.
Sub-order TUBICOLA. Inhabiting calcareous tubes.
ERRANTIA. The free-swimming, marine worms.
Branch MOLLUSCOIDEA. Animals with short, simple alimentary
canal; respiratory organs in front of
mouth.
Class BRYOZOA. Very small organisms living in colonies and
secreting a compound skeleton resembling
that of corals.
BRACHIOPODA. Much larger than Bryozoa; not in colonies,
but single; secrete a bivalved shell
each valve of which is symmetrical
about a median line. See page 208.
Branch MOLLUSC A. Bilateral, highly developed organisms with
heart and systemic circulation; body
enclosed in mantle; fleshy foot-like struc-
ture on under side; shells differ in the
different classes.
Class PELECYPODA. Known also as Lamellibranchs and
Bivalves; include such creatures as
the common clam, oyster, etc. Foot
hatchet-shaped; gills usually leaf-like.
SCAPHOPODA. With long, tapering, tubular shell.
GASTROPODA. Shells single, hence called Univalves;
shells saucer shaped or spiral; foot a
creeping or swimming organ. Snails
and related creatures.
CEPHALOPODA. Highly developed molluscs. Edges of
foot rolled up to form a tube through
which the water from the gill cavity
is ejected. Squids, nautilus, cuttle-
fish, etc.
ELEMENTARY GEOLOGY
Order NAUTILOIDEA. Free-swimming marine organisms with
straight or coiled shells. The shells
are divided into chambers by simple
partitions.
AMMONOIDEA. Like Nautiloidea, but the edges of the
partitions are puckered so that their
union with the shell wall is not simple
but complicated. Extinct.
BELEMNOIDEA. With a cigar-shaped internal shell.
Belemnites proper are extinct.
Branch ARTHROPODA. The higher invertebrate animals with
jointed legs.
Class CRUSTACEA. Breathe by gills; generally aquatic; many
limbs and segments.
Sub-class TRILOBITA. Crustacea with only one pair of
antennae and a very characteristic
three-lobed body.
EUCRUSTACEA. Two pair of antennae; non-tri-
lobite body.
Super-order PHYLLOPODA. Elongated body, laterally com-
pressed shell.
OSTRACODA. With bivalved shell covering the
whole body.
CIRRIPEDIA. The barnacles, etc.
MALACOSTRACA. The higher crustaceans with
a constant number of seg-
ments, 20 or 21.
Order SCHIZOPODA. Eyes on movable stalks.
DEC APOD A. With ten feet; lobsters, crabs, etc.
Class ACERATA. Body divided into two regions; breathe by
lung-books.
Sub-class MEROSTOMATA. The king crabs and related forms.
Order EURYPTERIDA. A group of peculiar extinct organ-
isms. See page 230.
Sub-class ARACHNIDA. The spiders, scorpions, mites, etc.
Sub-branch MYRIOPODA. Long-bodied, wingless arthropods
breathing by tracheae. The thousand-
legs, etc.
INSECTA. The insects.
Sub-kingdom VERTEBRATA. Animals with backbone.
Class AGNATHA. Fish-like forms but without jaws.
PISCES. The fishes. Long-bodied, aquatic; breathe by gills.
Sub-class ELASMOBRANCHII. Cartilaginous fish with several gill
clefts. Sharks, rays, and various
extinct groups.
HOLOCEPHALI. The chimeras, etc.
DIPNOI. The lung fishes.
TELEOSTOMI. Ganoids and scaly fishes.
Order CROSSOPTERYGII. With fringed fins.
ACTINOPTERYGII. With shortened fin axes and long
rays.
Class AMPHIBIA. Broad-headed animals without external scales
or plates; undergo a metamorphosis.
Order STEGOCEPHALIA. Extinct forms with plated cheeks.
CLASSIFICATION OF ORGANISMS 159
Class REPTILIA. Cold-blooded animals with no metamorphosis.
Order ANOMODONTIA. Primitive extinct forms.
SAUROPTERYGIA. Long-necked, extinct, aquatic rep-
tiles.
CHELONIA. The turtles.
ICHTHYOPTERYGIA. Short-necked, extinct, aquatic
reptiles.
RHYNCHOCEPHALIA. Primitive type of land reptile.
SQUAMATA. Elongated forms like the snakes and some
extinct water reptiles.
DINOSAURIA. A great group of extinct land reptiles.
CROCODILIA. Crocodiles, alligators, etc.
ORNITHOSAURIA. Extinct flying reptiles.
Class AVES. The birds.
Sub-class ARCII^EORNITHES. Peculiar extinct birds with teeth.
NEORNITHES. All other birds.
Order RATITS. Flat-breasted birds without the power of
flight.
CARINAT^E. Flying birds, with a crest on the breastbone.
Class MAMMALIA. The mammals. Warm-blooded animals; suckle
the young.
Sub-class PROTOTHERIA. Oviparous.
METATHERIA. Young born immature and carried in
a brood pouch. Kangaroos, etc.
EUTHERIA. Young capable of independent existence.
Order CETACEA. Whales.
SIRENIA. Manatees and dugongs.
EDENTATA. Ant-eaters, armadillos, and extinct forms.
UNGULATA. The hoofed animals. Horse, cattle, deer,
elephant, etc.
RODENTIA. The rodents. Beaver, hedgehogs, rats, etc.
CARNIVORA. The predaceous, flesh-eating mammals.
INSECTIVORA. Shrews, moles, etc.
CHIROPTERA. Bats.
PRIMATES. Lemurs, monkeys, man.
VEGETABLE KINGDOM:
Sub-kingdom CRYPTOGAMS. The lower plants in which reproduction
is effected by means of spores.
Branch THALLOPHYTA. Unicellular or multicellular plants of
simple construction. The larger forms
grow as flattened expansions which do
not show root, stem, and leaves as in
the higher plants.
Class ALG;E. Includes unicellular organisms of microscopic
size (diatoms and desmids), the red and brown
sea weeds, and the freshwater green and
blue-green weeds. \
FUNGI. The funguses. No importance as fossils.
Branch BRYOPHYTA. Spore-bearing plants composed of cellular
tissue which shows little differentiation.
By sexual reproduction a spore-case
arises in which the spores are asexually
produced. Mosses and liverworts, of
little importance as fossils.
i6o
ELEMENTARY GEOLOGY
PTERTDOPHYTA. The tissue is not evenly cellular through-
out the plant, but is partly differen-
tiated into special tissue which forms
longitudinal bundles and facilitates
the transmission of fluids. On this
account the pteridophytes are called
"vascular cryptogams." Ferns, horse-
tails, and club mosses.
Sub-kingdom PHANEROGAMS.
Branch GYMNOSPERM^.
Class CYCADALES.
GINKOAI.ES.
CONIFERALES.
Branch ANGIOSPERMS
Plants that reproduce by means of
seeds.
The most lowly of the flowering plants.
Primitive forms are scarcely to be
distinguished from the highest pteri-
dophytes. The name means "naked-
seeded," and is derived from the fact
that the seed is not enclosed in the
ovary.
These plants fade into the pteridophytes on
the one hand, and less clearly into conifers
on the other. Most existing cycads have
short trunks which bear a crown of leaves
resembling those of a tree fern. The bark
is marked by numerous leaf scars. The
leaves are large, pinnate, and of firm
structure. A cross section of the stem
shows many variations, but always there
is a large amount of pithy tissue often
alternating with rings of wood. These
plants are one of the sources of sago,
which is stored in the pithy tissue. Fossil
cycads are of great importance: they are
known principally from leaves, but also
from trunks and fruits.
Resemble cycads in the method of fertilisa-
tion. The foliage resembles that of the
maidenhair fern; they are called "maiden-
hair trees" in consequence.
Unlike the cycads these trees form long
tapering trunks from which branches
arise, either in whorls or irregularly. In
both cases the general effect of the
branching is to produce a tree of taper-
ing, cone-like outline. The leaves are
always small, frequently elongate; in
this respect the conifers differ strikingly
from the cycads.
The true flowering plants in which the
seed is enclosed in an ovary.
CHAPTER IV
THE ARCHAEAN OR PRE-CAMBRIAN
WHEN geologists first attempted to work out the history of
the world they naturally began with the rocks at hand in
England, France, or Germany: it was found that these rocks
contained sea shells and that they had clearly been laid down
on the sea bottom. It was presently found that the most con-
venient way of classifying them was by the character of the
life of the time as shown by the fossils, and gradually a scheme
of classification grew into shape in which the history of the
world was divided into great divisions, each with its own
types of life.
The lowest division was called the Palceozoic, or Time of
Ancient Life (from the Greek words palaios, ancient, and zoon,
an animal). Following the succession of formations down-
wards in the Palaeozoic, the lowest beds containing fossils
were named the Cambrian, and for a long time investigation
practically stopped at that limit. The rocks below were not
alone void of fossils, but often had such confused and com-
plicated arrangements that they seemed quite hopeless and
were set aside in despair as a "basal complex" or "funda-
mental complex." Something had to be done with them,
however, in the classification, and since they showed no
evidence of life they were called Azoic (without life), to bring
them into line with the "zoic" system.
Doubts arose, however, as to the real absence of life in
these older times because of the apparently sudden appearance
of the multitude of animals that swarmed in the Cambrian
sea; in consequence, some geologists suggested the name
Eozoic (dawn of life). As a compromise between the two
hostile views many writers used the term Archcean (ancient),
which implies no theory, and others the negative expression
Pre-cambrian. Both are still in good use.
It is not surprising that the classification of the troublesome
rocks below the Cambrian should long have been neglected in
L 161
162 ELEMENTARY GEOLOGY
Europe, since only small and scattered areas of them exist in
the countries where geology was earliest cultivated, and the
succession in Europe is very incomplete, except apparently in
Finland. Even in Canada, with the largest and best exposed
Pre-cambrian area in the world, there are still difficulties in
the classification, especially of the older and more meta-
morphosed parts.
The first serious attempt to subdivide the basal complex
was made by a Canadian, Sir William Logan, first Director of
our Geological Survey. He found a great thickness of steeply
tilted, crystalline rocks, mostly gneisses, underlying all others
along the St. Lawrence valley, and named them the Laurentian.
He divided the Laurentian into a lower part, the Ottawa gneiss,
and an upper part, the Grenville series, supposed to be the
younger of the two. Above rocks of this kind, on the north
shore of Lake Huron, a series of comparatively flat-lying and
unchanged sediments was named the Huronian.
For a long time this classification of the Pre-cambrian was
accepted as sufficient, not only in North America, but also
in Europe.
Later the name Keewatin was given to rocks west of Lake
Superior which had been included in the Huronian, but were
proved by Dr. Lawson to be older than the Laurentian, and
therefore far older than the original Huronian.
Still later it was found that a great series of sedimentary
rocks, younger than the Keewatin and Grenville series, but
older than the Huronian, existed near Lake Timiskaming, at
Sudbury and elsewhere. The gaps between these rocks and
those above and below are profound, great enough to allow
time for the elevation and destruction of mountain chains, so
that it was necessary to place them in a division by themselves.
The final result is the classification given on page 154,
which may, however, have to be revised in later years as
our knowledge of these obscure, half-obliterated pages of
the earliest history of Canada and the rest of the world
grows more complete.
In all the older writings on the geology of Canada, the whole
of the Pre-cambrian is included under the term Archaean;
but some American geologists use it only for the Pre-huronian
series, and put the Huronian and later series into the Algon-
ARCHAEAN OR PRE-CAMBRIAN 163
kian. This usage has not been adopted in Canada except,
sometimes, for parts of the western Pre-cambrian.
The terms Proterozoic and Archeozoic are used by some
good authorities to express ancient life relationships which
almost certainly existed, but of which there is little direct
proof.
In the account of the Archaean formations we shall dis-
regard the subdivision into Proterozoic and Archaeozoic and
begin with the oldest known formations, the Grenville and
FIG. 72. OUTLINE MAP OF CANADA SHOWING IN BLACK THE CHIEF AREAS
OF PRE-CAMBRIAN ROCKS
Note the "Canadian shield" surrounding Hudson bay and the smaller areas to
the east and west.
Keewatin, as shown in the table on page 154. To these a
third series will be added, the Coutchiching.
THE GRENVILLE SERIES
Logan considered the Laurentian (Ottawa gneiss) the oldest
of the Canadian rocks, since it underlies all others, and
believed that it consisted of metamorphosed sediments, the
banded structure commonly observed in gneisses being looked
on as evidence of stratification. It has been proved, however,
by later field work, especially since the petrographic micro-
scope came into use, that the granites and also most of the
Laurentian gneisses are eruptive masses, batholiths which
have domed up the Grenville series of the east and the
1 64 ELEMENTARY GEOLOGY
Keewatin of the west, sending dikes into them and splitting
off and carrying away fragments. It is certain, therefore, that
these underlying granites and gneisses are younger than the
overlying rocks, since the age of an eruptive rock is reckoned
from the time when it cooled.
Accordingly the Grenville and the Keewatin, probably
of about the same age, are the earliest of known rocks. As
the Grenville was studied first it may take precedence of
the Keewatin.
The most striking Grenville rock is crystalline limestone,
sometimes white, like coarse marble, but often grey or coloured,
and sometimes charged with minerals such as graphite, mica,
hornblende, augite, or serpentine. As this is the least resistant
rock of the series it is usually found in valleys and makes the
bed of rivers or lakes.
Along with the crystalline limestone and sometimes inter-
bedded with it, one generally finds gneiss or quartzite, the
former often containing pyrite, garnet, and graphite, while
the latter is generally glassy and more or less mixed with
garnet, feldspar, or other silicates.
The gneiss of the Grenville differs markedly in most cases
from the Laurentian gneiss, which is really a schistose granite :
it is often duller in colour, weathers rusty from the decay of
the pyrite, and may contain graphite or sillimanite, which are
not found in Laurentian gneiss. Analyses show that it has the
composition of a slate or shale.
The quartzite of the Grenville is not so widely found as the
other rocks, but is well seen at the Thousand islands.
Schistose conglomerate is occasionally mentioned as a
rock of the Grenville series, but it may really be a basal
conglomerate of a later formation and will not be de-
scribed here.
Most of the Grenville rocks, in spite of their crystalline or
schistose character, are really sediments, evidently water-
formed as sand or mud or limey materials, exactly as sediments
have been laid down in all the later ages of the world ; and it
is astonishing to find this earliest of formations presenting in
a disguised form all the common kinds of stratified rocks.
There are even suggestions of life in the graphite, the carbon
of which may have come from primitive plants, and the calcite
ARCH^AN OR PRE-CAMBRIAN 165
of the limestone which may have been formed of the hard
parts of animals.
At one time it was believed that a peculiar interbanding of
calcite and serpentine was a fossil protozoan which received the
name of Eozoon canadense, the Canadian "dawn animal";
but there is proof that this is a mistake, so that the evidence
for life in the Archaeozoic does not go beyond the carbon and
lime found in its rocks.
Closely associated with the Grenville there is an interesting
eruptive rock, nepheline syenite, apparently produced by the
emanations from later granites acting on the limestones. The
only corundum mined in Canada occurs in such syenites at
Craigmont, Ontario.
The Grenville in its greatest development forms a very thick
series of rocks, reaching, according to Adams and Barlow,
17,824 feet in Burleigh and Chandos townships of eastern
Ontario, and as much as 94,406 feet along the Hastings road,
50,286 feet being pure limestone. If the last estimate is
correct there are few, if any, limestone formations of later
ages to compare with it.
DISTRIBUTION OF THE GRENVILLE
These rocks are widely found from Lake Huron eastward
in southern Ontario and Quebec, extending along the southern
border of the " Canadian Shield" from Georgian bay to a point
beyond St. Maurice river at Three Rivers, Quebec, their
eastern boundary being somewhat uncertain. Rocks of a
similar kind, probably of the same age, are found in various
places toward the north-east in Labrador, especially along the
southern coast and in the north-east peninsula. Crystalline
limestones are largely developed also north of Hudson straits
in Baffin Land. The Grenville rocks, which are well displayed
in the Thousand Islands region, extend across the St. Lawrence
into the Adirondack mountains of New York, covering a wide
area, while similar rocks are reported from the states farther
east. Dr. Adams estimates the extent over which these rocks
are distributed at 83,000 square miles, and thinks that
originally they may have covered the whole region.
There are crystalline limestones and sedimentary gneisses
166 ELEMENTARY GEOLOGY
in the wide-spread Shuswap series of British Columbia, the
oldest rocks in the province, which may be Grenville in age,
though at such a distance and in the absence of fossils this
cannot be certainly proved.
The oldest sediments found in the Pre-cambrian of Scot-
land, Scandinavia, and Finland much resemble the Canadian
Grenville, and rocks of the same type are known in India and
in southern Brazil ; so that in several continents the geological
record begins with sediments, now metamorphosed into crys-
talline limestones with graphite, garnetiferous gneiss, and
quartzite. Whether they are all of the same age, however,
there is at present no means of determining.
ECONOMIC FEATURES OF THE GRENVILLE
The easily weathered Grenville limestones provide some of
the best soils of south-eastern Ontario and the adjacent parts
of Quebec. The limestones themselves furnish handsome
marble near Bancroft and elsewhere, and they are burnt for
lime when pure enough. Graphite, phlogopite or amber mica,
talc, magnesite, and corundum are mined in the Grenville to
an important extent ; and in former years apatite (phosphate)
and iron ore (magnetite) were obtained in considerable quan-
tities from deposits connected with the Grenville series.
ATTITUDE OF THE GRENVILLE
Grenville rocks are apt to run as long bands between areas
of gneiss, since they commonly form synclinal troughs caught
between the batholiths of the Laurentian. These bands may
run out as tongues or may change their strike and enclose
oval areas of gneiss. Usually the Grenville rocks have steep
dips, as might be expected under the circumstances. The
originally flat-lying Grenville sediments were domed up into
mountain ranges by the rise of the batholiths beneath, but
these ancient mountains have usually been so far eroded as
to leave only the lower parts of the Grenville syncline, pro-
tected by the more resistant gneisses on each side. Rarely,
as at St. Jean de Matha in Quebec, do we find the Grenville
rocks lying nearly horizontal at the top of broad low domes
which have escaped complete destruction.
ARCHAEAN OR PRE-CAMBRIAN 167
THE KEEWATIN SERIES
THE KEEWATIN OF THE TYPE LOCALITY
The Keewatin rocks in their typical locality on Lake-of-the-
Woods are strikingly different from those of the Grenville
series, consisting mostly of volcanic materials of various kinds
with only subordinate sedimentary deposits, or, in some areas,
none at all. The sedimentary rocks which do occur are chiefly
black slates and greywacke, which have very little in common
with the limestones, gneisses, and quartzites of the Grenville,
though they seem to occupy about the same position in the
west as the Grenville in the east. Old lavas like the western
Keewatin rocks have been found conformably beneath Gren-
ville rocks in eastern Ontario by Miller and Knight, however,
confirming the conclusion that the two series are of about the
same age. *
The Keewatin was a time of great volcanic eruptions,
which took place, at least in part, beneath the 'sea, as is
proved by the "pillow" or "ellipsoidal" structure often
observed. The majority of the lavas were very basic, such as
basalts, and have since been weathered into greenstones, or
have been squeezed or rolled out into green schists. In most
cases the green mineral of the schists is chlorite, but near the
granite contacts it may be changed to hornblende. In places
there are amygdaloidal lavas, and also ash rocks or agglo-
merates made of volcanic bombs and lapilli.
In smaller amounts one finds rhyolites, now often trans-
formed into pale schists, with mica in the form of sericite.
In addition to the volcanic rocks there are dikes, sheets, and
bosses of basic and acid rocks related in various ways to those
described before, and also dikes of pegmatite and granite
coming from the later Laurentian batholiths.
The sediments found in subordinate amounts include mainly
greywacke and slate, the latter rock sometimes black and
charged with carbon. Conglomerates, also, have been ascribed
to the Keewatin, but it is probable that they really belong to
the next geological period.
The only economic mineral found in the original Keewatin
region is gold, which occurs in many places at or near Lake-
168 ELEMENTARY GEOLOGY
of-the- Woods, as well as Rainy lake, but has nowhere been
mined with profit.
THE KEEWATIN SERIES IN OTHER REGIONS OF CANADA
A band of Keewatin interspersed with granite, gneiss, and
later sediments extends to Thunder bay. It includes lavas,
ash rocks, and schists like those just mentioned, and also
extensive iron ranges, as at Hunter's island and the Mattawin
river, in which banded jasper plays a large part. In this case
the iron occurs as hematite or as hematite mixed with mag-
netite. Thus far the typical iron ranges of the region have
supplied no ore, though important mines occur near Ely
in Minnesota, on the Vermilion iron range, just south of
Hunter's island. A large deposit of magnetite rather low in
grade, and sulphurous, occurs, however, as lenses in a ridge
of greenstone at Atikokan, where some mining has been done,
the ore being smelted at Port Arthur.
The next important band of Keewatin appears at Michi-
picoten bay, on the north-east side of Lake Superior, running
first eastward, then curving north, and finally running for fifty
miles or more to the west. In addition to lavas, often showing
typical pillow structure, there are pale-green schists with
carbonates, and ridges of the iron formation of an unusual
kind, in many cases including great deposits of siderite
associated with pyrite. By the weathering of these materials
the Helen iron ore deposit was formed, the most important
thus far worked in Canada. The ore is partly limonite and
partly hematite, and pyrites has been obtained from the
same mine. A large deposit of siderite, which when roasted
gives a fair ore, is now worked at the Magpie mine, a few
miles away from the Helen mine.
Large areas of Keewatin occur north of Sudbury at Moose
mountain, where an iron mine has been worked, and extend
with interruptions of later eruptives and sediments of the
Timiskaming series to the Porcupine region, where some
valuable gold deposits are enclosed partly in these and partly
in later rocks. In addition large or small areas of rocks like
the Keewatin with lavas and iron formation have been found
widely scattered over the Archaean to the north-east and
ARCH^AN OR PRE-CAMBRIAN 169
north-west of James bay. Probably more of them will be
discovered as the regions farther north are explored.
THE KEEWATIN SERIES IN OTHER COUNTRIES
The Keewatin bands in western Ontario sometimes cross
the boundary and extend into Minnesota and other neigh-
bouring states, in some places furnishing large deposits of
iron ore, but away from the Lake Superior region Keewatin
rocks have not been found with certainty. It is of interest to
note, however, that interbanded silica and iron ore are found
in connection with the most ancient rocks of several countries,
as in Brazil, South Africa, Australia, and Scandinavia. What-
ever the source of these masses of silica and iron oxide, the
process of forming them seems to have been wide-spread in
the world in the earliest known ages, while in later times they
are rare or entirely absent.
THE COUTCHICHING SERIES
When field work was carried eastward from Lake-of-the-
Woods to Rainy lake it was found that sedimentary rocks
occur, in some places on a large scale, beneath the Keewatin
lavas and schists of the latter region. They are widely differ-
ent from those of the Grenville and consist of monotonous
grey gneisses and mica schists often containing garnets
and staurolites. The Coutchiching represents muddy or
sandy sediments.
The sedimentary and volcanic rocks of the series which
have been described must have been laid down upon a floor
of solid rock, the bottom of the sea in those days, but it is
very surprising that no such floor has ever been discovered.
It seems to have been destroyed and worked over into other
forms during the tremendous changes that followed.
THE LAURENTIAN
In every known region of the Keewatin and Grenville the
rock beneath consists of gneiss or granite which has welled up
in a molten state, forming batholiths and doming up the over-
170 ELEMENTARY GEOLOGY
lying lavas and sediments, whose remnants remain as synclinal
meshes or tongues between the greatly eroded masses of gneiss.
Strictly speaking, eruptive rocks should be looked on as in a
sense accidental, and not to be included in the divisions of a
time scale; but the building of batholithic mountains over the
immense area shown in our Archaean region marks an event of
great importance in the geological history of the country, and
probably demanded a vast length of time. It seems desirable,
then, to take up the Laurentian as marking a long-continued
and most significant series of operations profoundly affecting
Canadian conditions for all later time and forming the sub-
stratum of the great Canadian Shield, about which the con-
tinent has been built up, largely of materials derived from the
Laurentian mountains.
The rocks of the Laurentian have mainly the composition
of granite, granodiorite, or syenite, with smaller amounts of
gabbro or diorite ; but usually these materials have a schistose
or banded structure and are termed gneiss. The rocks are
mostly coarse-grained and often contain porphyritic feld-
spar crystals, and, in many cases, they have been sheared
into "porphyritic granitoid gneiss," a very common phase
of the Laurentian.
Laurentian batholiths are often oval, but sometimes irre-
gular in shape where several upwellings have combined, and
have a schistose structure parallel to the curving edge,
changing inwards to the ordinary structure of granite. They
may be of all sizes, from a few miles to fifty miles in longest
diameter, as on Rainy lake; and their general arrangement
runs roughly north-east (5o°-8o° east, of north), indicating the
direction of the great mountain chains of which they formed
the cores. The steeply dipping schists surrounding many of
the larger batholiths outline the foundations of ranges which
may have been higher than the present Rockies.
Cutting all the rocks mentioned there are dikes of coarse
pegmatite, the last of the granitic materials to crystallise,
often with giant crystals of feldspar and other minerals. Two
large dikes have been worked in eastern Ontario as mines of
potash feldspar, supplying thousands of tons for the use of
potteries. In a general way, however, the Laurentian is very
barren of valuable products except in a few places where
ARCHAEAN OR PRE-CAMBRIAN 171
granite is quarried for paving or other purposes. As mapped
on the Canadian Shield the Laurentian covers an enormous
space, probably more than 1,000,000 square miles, though
there is reason to believe that similar batholithic upheavals
took place at a later age. As the rocks of the two ages are
much alike, the two sets of granites and gneisses have been
separated only in a few areas which have been mapped
in detail.
OTHER REGIONS WHICH MAY BE LAURENTIAN
There are other large areas which have the character of the
Laurentian and underlie unconformably all formations except
the very oldest in the Selkirk and Gold Range mountains of
British Columbia, and smaller ones in Nova Scotia and New
Brunswick. Outside of Canada the Laurentian extends south
at the Thousand islands and forms a large part of the Adiron-
dack mountains, and similar ancient granites and gneisses
occur in the Appalachians and in other regions of the United
States. Rocks of the Laurentian type exist in Greenland, and
cover a large part of the Scandinavian Shield in Norway,
Sweden, and Finland, and a smaller tract in the Highlands of
Scotland. It is probable that these regions were once directly
connected with the Canadian area.
All the great subdivisions of the world include areas of
granite and gneiss at the base of the geological succession,
occupying apparently the same position as our Laurentian,
and similar rocks have been found in drill holes beneath
hundreds and even thousands of feet of later rocks. They
occur, for instance, at noo or 1200 feet beneath the city of
Toronto. It seems probable that they everywhere underlie
the oldest sedimentary rocks and, therefore, form the universal
basement for the later geological formations.
THE POST-LAURENTIAN INTERVAL
Before the next series of sedimentary rocks was laid down
there must have been a tremendous interval to permit of the
destruction of the great mountain ranges of the Canadian
Shield. This seems to have been a dry land period when the
172 ELEMENTARY GEOLOGY
weather, running water, perhaps also frost or ice, did effective
work, for the overlying materials, Grenville or Keewatin, of
the batholithic mountains seem to have been largely destroyed
and the granite cores deeply eaten into. What became of the
materials we do not always know, but in any case the basal
rocks of the next great period of known geological time
consist of debris that must have come from this destruction.
How long the interval of erosion lasted there is no way of
estimating, but it must have meant millions of years.
THE SUDBURY OR TIMISKAMING SERIES
On the erosion surface of the ancient mountain area a great
succession of sediments — conglomerates, sandstones, grey-
wackes, and shales — was laid down, now metamorphosed into
schist conglomerate, quartzite, slate, or schist, etc. The
thickest known development of the series is in the Sudbury
region, which has been more carefully studied than the others
and may be considered typical.
Conglomerate is not extensively found in this series near
Sudbury, but when it occurs it consists of well-rounded
pebbles and stones of various kinds with a cement like
greywacke. The lowest rock of the series is the Copper Cliff
arkose, often so much recrystallised as to resemble syenite or
felsite. It was formed under conditions which allowed granites
or gneisses to crumble without much decay of the feldspars,
so that the climate was probably either desert-like or cool and
moist, the latter being more likely.
Then follows greywacke with thin slaty layers very
uniformly stratified with coarser and finer bands, perhaps
representing the change of seasons, and finally quartzite in
thick beds, sometimes showing cross bedding. The whole
series has been tilted, often at an angle of 45° or more, and
the total thickness is not less than 20,000 feet.
Towards the end of Sudburian time there were eruptions
of very basic lava, showing pillow forms and also amygdaloids.
All of the rocks mentioned are older than the adjoining
granites and gneisses, which often contain fragments of the
sediments, and penetrate them in elaborate ways. In such
ARCHAEAN OR PRE-CAMBRIAN 173
cases the sedimentary rocks are more or less metamorphosed
into schists or even into gneiss.
The Sudbury rocks just described seem to be of the same
age as the Timiskaming series to the north and east, near
Lake Timiskaming, and at the gold mines of Porcupine.
Except that there is more conglomerate, the rocks are alike
in almost every respect, and they have been cut by granites
as at Sudbury.
The Pontiac series in Quebec has similar relations, and this
is true also of the Dore conglomerate on Michipicoten bay.
FIG. 73. TTMISKAMING SERIES, PORCUPINE, ONTARIO
Here there are schistose conglomerates several thousands of
feet thick, enclosing boulders of a great variety of rocks, such
as granite, greenstone, and iron formation, sometimes reach-
ing diameters of two or three feet. This conglomerate is
possibly of glacial origin, but the stones enclosed in it are
too much squeezed and rolled out to give the final evidence
of ice action.
Much farther to the west, between Thunder bay and Lake-
of- the- Woods, a great series of sedimentary schists and con-
glomerates, called by Lawson the Seine series, reminds .one
very much of the Sudburian. It too is upheaved and cut by
later granites which have often greatly metamorphosed the
sedimentary rocks.
If all of these areas belong to the same period, which is
174 ELEMENTARY GEOLOGY
probable, the Sudbury and related series represent a thick and
wide-spread group of coarse sediments, probably laid down in
shallow seas after the original land surface had sunk beneath
the waters, perhaps formed as delta materials near the mouths
of great rivers.
The Hastings series in eastern Ontario, sometimes considered
a less metamorphosed part of the Grenville, is believed by
Miller and Knight to be the equivalent of the Timiskaming
series, since a conglomerate at its base includes pebbles derived
from the Grenville. The Hastings series contains limestones,
which are infrequent in the Sudbury and Timiskaming series.
Rocks of the age just described have not yet been recognised
in other parts of America or in other continents.
GENERAL FEATURES OF THE EARLIER
PRE-CAMBRIAN
All the series of rocks thus far mentioned, both sedimentary
and eruptive, have undergone great changes since they were
first formed, and are now so metamorphosed by mountain-
building activities, folding, faulting, shearing, and penetration
by later eruptives, that their original character is often hard
to determine. The older series, such as the Grenville and
Keewatin, have of course suffered more than the Sudburian,
but all have been more greatly changed than the later
Pre-cambrian, which remains to be described.
In spite of this blurring of the record there is reason to
believe that the condition of the world was not greatly
different from that of later ages. The world was not intensely
warm, as old theories suggested, for water was at work during
the whole time. There were mountain-building thrusts, great
volcanic eruptions, and also the slow wearing down of the
mountains, but the same type of work has been going on ever
since, and so far as geologists know, with much the same
intensity. Except as to life, of which we know nothing
positively, it is surprising to find our earliest glimpses of the
earth so like conditions which reach even to the present.
ARCHAEAN OR PRE-CAMBRIAN 175
THE ALGOMAN OR POST-SUDBURIAN GRANITES
Granites and gneisses seem everywhere to have invaded
and tilted or folded or domed up the sedimentary rocks just
described, very much as the Laurentian eruptives acted upon
the Grenville and Keewatin. It is, in fact, often very difficult
to distinguish the two sets of deep-seated eruptives, each of
which seems to have formed batholithic mountains. Dr.
Lawson has given these later granites and gneisses the name
of Algoman. Up to the present there are only a few localities
where they have been separated from what was formerly
called Laurentian. The Algoman granites and the dikes sent
off from them are credited with supplying the gold of most of
the mines in northern Ontario, especially those of Porcupine,
which include one of the greatest gold-mines in the world,
the Hollinger mine, as well as several other important deposits.
THE POST-ALGOMAN INTERVAL
Following the Algoman eruptions of granite came a great
period of erosion when at least the southern part of the
Canadian Shield was dry land, and was slowly attacked by
the epigene forces and ultimately was reduced to a peneplain
with a surface of gently rounded hills and shallow valleys.
It appears as if this process of levelling was so thorough that
all later weathering and destruction of the surface during dry
land conditions have not greatly changed the character of
the country.
THE HURONIAN SERIES
After what appears to have been the longest break in the
Pre-cambrian history of Canada, the Huronian begins as
coarse sedimentary rocks formed at or near the southern edge
of the shield, with the greatest development in the typical
locality on the north shore of Lake Huron. These rocks were
mapped on a small scale more than sixty years ago by Logan's
assistant, Murray; but the country was covered by forests
176 ELEMENTARY GEOLOGY
and difficult to traverse except by canoe routes, so that his
work was more or less imperfect. Recent work by Collins of
the Geological Survey shows that the Huronian really con-
sists of two divisions separated by an important discordance,
the lowest being named the Bruce series and the upper the
Cobalt series.
The Bruce series begins with 1000 to 2000 feet of white
quartzite, often conglomeratic at the base, followed by thinner
formations of conglomerate, limestone, and greywacke; it
ends with 1000 feet of white quartzite and 40 feet of grey-
wacke, the whole series having a thickness of 3000 feet or
FIG. 74. STRIATED STONE FROM COBALT TILLITE
more. Most of the beds are water laid, though there are
hints of dry land conditions in some deposits.
After a somewhat important break implying a good deal
of erosion of the Bruce series, the Cobalt series commences
with a boulder conglomerate which is really a tillite or ancient
boulder clay. This is, of course, a continental formation made
under arctic conditions and implies an important glacial
period, the earliest certainly proved in the history of the
world. This basal conglomerate or tillite has furnished good
ARCHAEAN OR PRE-CAMBRIAN 177
specimens of striated stones at Cobalt and two other places;
and its great boulders, often far from their source, with other
features closely like the effects of ice in other ages, support
this evidence.
The tillite is followed by 600 or 800 feet of white quartzite,
nearly 3000 feet of "slate conglomerate," and thousands of
feet of red or white quartzite, including the showy jasper
conglomerate with red pebbles in a white ground. Then
come 200 feet of cherty limestone and 400 feet of white
FIG. 75. TILLITE (BOULDER CONGLOMERATE) OF COBALT SERIES
RESTING ON KEEWATIN GREENSTONE, COBALT, ONTARIO
quartzite, the whole series measuring probably more than
12,000 feet in the region north of Lake Huron.
The basal tillite of the Cobalt series, or Upper Huronian,
has been followed from the typical Huronian region to Cobalt,
and is believed to occur at Chibougamau and at other points
in the north and north-east, so that it seems to be much more
widely spread than the Bruce series, which has not been found
with certainty away from the typical Huronian region.
Among the Huronian rocks the limestone often looks
comparatively modern and suggests animal life, though no
fossils have yet been found in it, unless the limestone of
Steeprock lake in the Seine River region far to the west is
considered to be of this age. In the Steeprock limestone two
178 ELEMENTARY GEOLOGY
or three species of Atikokania occur, an organism supposed
to be related to the sponges or to the somewhat problematic
Archceocyathina of the Cambrian. These are large fossils and
do not suggest the earliest beginnings of life. Black carbon-
aceous slate occurs in a thin bed at Cobalt, suggesting, perhaps,
plant life as the source of carbon.
Huronian rocks extend south of Lakes Huron and Superior
into Michigan, Wisconsin, and Minnesota, and are of im-
portance as containing iron ores. Formations considered
Huronian are found also in Newfoundland, and one or two
obscure fossil forms have been reported from them. Whether
the "Beltian" rocks of the west are Huronian or not is
uncertain. They will be mentioned later. Pre-cambrian
sediments not greatly metamorphosed occur in various parts
of the world and may be of Huronian age, but a certain
correlation is impossible at such great distances in the absence
of fossils.
THE ANIMIKIE SERIES
The Animikie begins, it is believed, with a great trans-
gression of the sea over the Canadian Shield. Rocks of this
age were first described from the Thunder Bay region, where
they have a thickness of 1500 or 2000 feet and rise as cliffs
of chert and slate with one or more great sheets or sills of
diabase, forming the flat-topped hills so characteristic of the
north-east side of the Lake Superior coast. Farther south-
east sandstone or quartzite shows beneath these rocks, and at
some' points there is a little impure iron ore. A thin con-
glomerate underlies the formation at a few points on Thunder
bay, resting on the upturned edges of the Keewatin and
Lauren tian schists and gneisses. Silver has been mined at
several places in these rocks and the dikes that intersect them,
the mine on Silver islet being worked in the richest deposit.
The continuation of the Animikie into Minnesota supplies
the great iron deposits of the Mesabi, perhaps the most
important in the world.
The thickest group of rocks ascribed to the Animikie is the
Whitewater series enclosed as a basin within the nickel-bearing
eruptive of Sudbury. This consists of a boulder conglomerate,
ARCH^AN OR PRE-CAMBRIAN 179
followed by tuff, black slate, and sandstone, the whole reach-
ing a thickness of 9450 feet. The slate is rich in carbon, like
the black slate at Kakabeka falls near Fort William ; and
veins of anthraxolite, much like anthracite in appearance and
composition, are found in both places. The shale was probably
once bituminous, suggesting life at the time, and anthraxolite
was pitch which has since lost its volatile constituents. This
material has several times roused false hopes of coal mines.
Several other regions in northern Canada display rocks
like the Animikie, but usually associated with volcanics and
sandstones belonging to the next age. They are found along
the east shore of Hudson bay, in the northern part of Labra-
dor, and near Great Bear lake, and in many places include
iron ores of a low grade.
The rocks of the Animikie, when not modified by later
sheets of diabase, look very modern, so that fossils might be
expected, though none have been found with certainty. They
often lie nearly flat and are seldom folded except in the in-
terior of the Sudbury nickel basin, where collapse has caused
compression, forming a number of narrow anticlines. Often,
however, these beds have been faulted and the blocks .gently
tilted, as near Port Arthur and Fort William.
The Animikie has not been reported from other countries
except in the states to the south and west of Lake Superior,
in the iron region.
THE KEWEENAWAN SERIES
After a considerable break the Keweenawan follows the
Animikie, but without much angular discordance. This
appears to have been a time of emergence of the land, often
with immense outpourings of lava, probably equalling in this
respect the Keewatin. A basal conglomerate, sometimes
bouldery, may rest upon the Animikie, as near Thunder bay,
or else upon the Lauren tian or the Keewatin; and this is
followed by white and red sandstones, limestones, and shaly
rocks, the whole having a thickness of 1300 or 1400 feet near
Thunder bay. The rocks show cross bedding and mud cracks,
the feldspars in some of the sandstones are little weathered,
i8o ELEMENTARY GEOLOGY
and red colours are common — all features suggesting con-
tinental and probably desert conditions.
The sedimentary rocks just mentioned are cut by many
dikes and are interbedded with sills of diabase, and resting
upon them at various places on the north and north-east
shores of Lake Superior there are thousands of feet of lavas.
These are mainly basic, the equivalents of the modern basalts,
but there are also quartz and feldspar porphyries and felsites,
representing the modern rhy elites. Along with the lava flows
there are conglomerates and sandstones in comparatively
small amounts, formed of contemporary volcanic materials
such as the porphyries.
The lavas are often highly amygdaloidal and with uneven
slaggy surfaces, but show no pillow structure. The amyg-
daloids contain a variety of minerals, including agates,
thompsonites, etc., which make pretty ornamental stones;
and also native copper in small amounts.
While copper has not been mined profitably on the Canadian
side of Lake Superior, some of the most important copper
mines in the United States have been worked on Keweenaw
point in Michigan.
The volcanic series has a thickness of 11,230 feet on Michi-
picoten island and of 16,208 feet at Mamainse near the east end
of the lake, but is twice or three times as thick in Michigan.
The Lake Superior Keweenawan has been more thoroughly
studied than that of any other area, but red sandstones and
conglomerates, generally with lavas which are often copper-
bearing, occur near Lake Athabasca and Great Slave lake,
and cover a very large area east of Great Bear lake and
near the suggestively-named Coppermine river on the Arctic
coast of Canada, whence the Eskimos in early days obtained
native copper for tools and weapons.
While the Keweenawan lavas have not yet furnished much
copper in Canada, it is believed that eruptive rocks of the
same age and origin have been of great importance in pro-
viding the ores of several mining regions of northern Ontario.
This is probably true of the great boat-shaped sill of riorite
and micropegmatite with which all the Sudbury nickel-copper
ores are associated, and also of the diabase sheet with which
the rich silver veins of Cobalt are connected.
ARCHAEAN OR PRE-CAMBRIAN 181
Undoubted Keweenawan rocks are not known beyond the
Canadian Shield except in the states bordering on Lake
Superior. Sandstones and conglomerates, probably of desert
origin, called the Torridonian, occur as the latest Pre-cambrian
in the highlands of Scotland, and similar rocks are found
in other continents as well as Europe.
THE WESTERN PRE-CAMBRIAN
Beside the vast area of Pre-cambrian of the Canadian Shield,
not far from 2,000,000 square miles in area, there is another
Pre-cambrian region, narrow and long, extending from south-
east to north-west as the central axis of the Cordilleran
mountain chains, making up most of the Purcell, Selkirk,
and Gold ranges of British Columbia. This area has been
studied in much less detail than parts of the Pre-cambrian
of Ontario and Quebec, and the age relations are much less
certain; so that it seems wiser to take up these formations
separately instead of attempting to include them under the
subdivisions known in eastern Canada. Two subdivisions are
generally recognised : a lower one, called the Shuswap series,
which has been intruded by batholiths of granite or diorite;
and an upper one, commonly called the Beltian, from a thick
series found in the states to the south and referred to the
Algonkian by most American geologists.
THE SHUSWAP SERIES
The Shuswap series was so named by Dr. Dawson, who
thought it equivalent to the Laurentian or Grenville of
eastern Canada. It includes various schists, sedimentary
gneisses, quartzite, and crystalline limestone, much meta-
morphosed by the granites and other eruptives which pene-
trate them, or perhaps by the depth to which they were
formerly buried, causing regional metamorphism. Professor
Daly thinks the latter is the true cause. These rocks rather
closely resemble the eastern Grenville, and sometimes contain
graphite. Daly puts their thickness at 29,900 feet. The
granites and eruptive gneisses which penetrate them have
the look of Laurentian rocks.
182 ELEMENTARY GEOLOGY
THE BELTIAN SERIES
The Beltian rests unconformably on the Shuswap series and
consists of sediments which have been much less metamor-
phosed. Dawson and Daly divide them into a lower part, the
Nisconlith series, and an upper part, the Selkirk series. The
Nisconlith is made up of quartzites, slates, and limestone,
the last rock in small amounts. The Selkirk series includes
similar rocks, but less metamorphosed. The total thickness
of the Beltian section is given at 32,752 feet. Most of these
rocks seem to have been laid down under water, but there are
many instances of beds containing ripple marks, mud cracks,
and casts of salt crystals, implying shallow water or dry land
conditions, perhaps even a desert climate.
It is probable that the Beltian rocks were laid down in a
great geosyncline, running about north-west and south-east,
and sinking gradually as the beds were deposited.
Although many of the Beltian rocks of British Columbia
are little changed and closely like the overlying Cambrian, no
fossils have been found in them. Very similar sedimentary
rocks in Montana, to the south, have been found by Walcott
to contain a few fossils, the best known being an arthropod
named Beltina, an animal fairly high up in the scale of life hi
spite of the fact that it occurs 7000 feet below the base of the
Cambrian. Why fossils should be so very rare in these
sediments is one of the puzzles of historical geology.
Rocks like the Beltian occur for a long distance south of
the boundary and are found in the Grand Canyon of the
Colorado in Arizona.
It is probable that the Beltian beds were deposited later
than the Sudbury or Timiskaming series, since they have not
been invaded by batholithic areas of granite and gneiss: but
whether they correspond to the Huronian, the Animikie, or
the Keweenawan, or perhaps to more than one of these
divisions, there is no means of deciding.
CONDITIONS IN THE LATER PRE-CAMBRIAN
Except near the southern edge of the Canadian Shield, the
rocks of the Huronian and later series are generally little
changed and their record is easily read. The boulder clay or
ARCHAEAN OR PRE-CAMBRIAN 183
tillite of the Cobalt series is as typical and well preserved
as that of the Permo-Carboniferous, which came millions of
years later, and is just as suggestive of chill ice fields and
wintry blizzards as the Pleistocene boulder clay of Ontario
in a period just before the present. There are, too, in the
Keweenawan clear proofs of desert heat and drought with
sand storms and withering winds as in the Sahara; but most
of the sediments show moderate conditions, flowing rivers,
waves that left ripple marks, the effects of weathering, all
like the familiar surroundings of the present, with perhaps a
more wide-spread volcanic activity in Canada during the
Keweenawan than at any later time.
Our knowledge of the life of the Pre-cambrian world, how-
ever, is still most meagre. Not a dozen species of plants or
animals are known from the many thousands of feet of
sediments laid down on sea bottoms just like the present.
There is nothing to justify a prophecy that the shallow
waters would swarm with living beings in the next period
of geological time.
CHAPTER V
THE PALAEOZOIC ERA— THE CAMBRIAN PERIOD
THE Pre-cambrian era is followed by another long era to which
the name Palceozoic is given, on account of the ancient char-
acter of all the life of the time. Between the beginning and
the close of the Palaeozoic vast physical changes took place,
and extensive development occurred in the animal and
vegetable worlds. The duration of the Palaeozoic was so long
and the physical and faunal changes so great that the era is
easily divided into a number of periods. It is proposed to
consider first these periods one by one, in order that the
student may become acquainted with the march of events
before discussing the Palaeozoic as a whole; a summary of
Palaeozoic history is deferred, therefore, until after the various
periods have been studied.
The lowest division of the Palaeozoic group of rocks is
known as the Cambrian system, and the same term is applied
to the time during which these rocks were deposited — the
Cambrian period. The name is derived from "Cambria," the
Roman name for the northern part of Wales.
Time is continuous; we can conceive of no breaks in the
continuity of time. Similarly there is every reason to believe
that sedimentation and the consequent production of strati-
fied rocks has likewise been continuous from the inception of
geological time to the present. It is well for the student to
understand clearly at this point that the Cambrian is separated
from the Pre-cambrian, not by the failure of geological pro-
cesses to make a record of the interval, but by the failure of
man to find that record. It is true, nevertheless, that nearly
everywhere where Cambrian rocks are found they rest uncon-
formably on the Pre-cambrian, indicating an interval of time
which is one of the most marked in all geological history.
Even this pronounced break in our earth's history is being
bridged by advancing knowledge, for the Lower Cambrian
rocks of southern British Columbia rest with scarcely a
perceptible disconformity on the earlier Pre-cambrian strata.
184
THE PALEOZOIC ERA 185
PHYSICAL EVENTS IN NORTH AMERICA DURING
THE CAMBRIAN
Very little is known as to the size and shape of the North
American continent at the beginning of Cambrian time, but
it was probably larger than at present, and certainly of very
different shape. We have every reason to believe, however,
that the Cambrian began, as far as certain and visible record
is concerned, during a downward folding of the continent
and a consequent invasion of the sea along a comparatively
narrow axis extending from California northward through
eastern British Columbia to the Arctic ocean. This depression
is called the Cordilleran trough.
Simultaneously, or perhaps a little later, a similar narrow
depression developed from the Gulf of Mexico to the maritime
provinces of Canada (Appalachian trough). Most of the time
during which the continental seas maintained this lineal
arrangement is known as Lower Cambrian. American geo-
logists refer to it as Waucobian, but the student must remem-
ber that the two terms are synonymous for North America
only. The geologists of the world have not adopted the
name Waucobian to replace the older term, Lower Cambrian,
in its world- wide application.
The subsidence of the continent, foreshadowed by the
formation of the two troughs .in the Lower Cambrian, was
continued in Middle Cambrian time, and the waters of the
Pacific ocean were permitted to extend beyond the limits
of the Cordilleran trough and to cover a large part of the
continent south and west of the Great Lakes. At the same time
the Atlantic waters advanced into narrow troughs in the
Acadian region. The strong development of Middle Cambrian
strata in the maritime provinces has led to the adoption of
the name Acadian for the Middle Cambrian of North America.
A more or less complete withdrawal of the sea marks the
close of Middle Cambrian time, but a submergence of still
greater extent followed and resulted in the oceanic waters
covering about 31 per cent, of the present area of the con-
tinent, The terra Croixian is applied by American geologists
i86
ELEMENTARY GEOLOGY
to the Upper Cambrian epoch because rocks of this age are
well developed on the St. Croix river in Wisconsin.
Maps may be drawn to show the distribution of land and
water at any time in the past. Such maps are known as
palceogeographic, and are not to be confused with geological
maps, which indicate the geographical extent of the various
FIG. 76. PAL^OGEOGRAPHIC MAP OF NORTH AMERICA IN
LOWER CAMBRIAN TIME
The white areas are land; the vertically lined areas were covered by the sea in the earliest
Lower Cambrian; the horizontally lined areas were covered by the sea in the later Lower
Cambrian time. From Pirrson and Schuchert, " Textbook of Geology."
formations. Geological maps are drawn from ascertained
facts: palaeogeographic maps are constructed upon data of
many kinds — the known extent of the rocks, their position,,
their physical characteristics, the variations in fauna indi-
cating migrations of animals and plants, and many other
considerations.
The chief value of palaeogeography to the beginner is that
THE PALAEOZOIC ERA 187
a general conception of the distribution of land and water at
a given time enables him to deduce the present position of the
strata deposited during that time. It may be generally stated
that sediments are always accumulating in off-shore seas.
Consequently, knowing the shore line during a given time, we
may safely conclude that deposits of that age were formed in
the adjoining sea. It does not necessarily follow that we shall
always find them in that locality now, as they may have
been covered by subsequent strata or removed by erosion.
It does follow, however, that rocks of a given age can be
found- only where comparatively shallow seas existed at the
time in question.
Applying these general principles to the Cambrian rocks of
North America, we find an explanation of the great gap
between the Pre-cambrian and the Cambrian in the fact that
the off-shore position was farther out to sea than at present.
The continent has not yet been sufficiently elevated to bring
into view the rocks formed during this time. As we are unable,
therefore, to decipher the history of this period, we have fallen
into the habit of calling it an "interval." Such intervals,
numerous in the course of geological history, are merely
unread passages in the unfolding tale of the earth: they do
not represent breaks in the continuity of sedimentation. The
whole history has been written, leaf by leaf, in the book of the
rocks; unfortunately, up to the present, many of the leaves
have not been found, and, more unfortunately, many of them
probably will never be found.
It is significant, also, that it is the existence of these gaps
that enables us to divide the history of the earth into eras
and periods. , To a certain extent, therefore, our geological
subdivisions are founded on a lack of knowledge; but this
thought must not be carried too far, as the unread intervals
correspond to great physical events in the history of the earth.
THE CAMBRIAN SYSTEM IN CANADA
We have seen that at the close of Keewatin time the eastern
part of Canada was thrown into great folds with a general
north-east trend; these folds have persisted to the present
i88
ELEMENTARY GEOLOGY
day. In the Lower Cambrian, and more particularly in the
Middle Cambrian, the waters of the Atlantic ocean invaded
the troughs between these folds; in consequence, we find
narrow belts of Cambrian rocks running in a general north-
east direction in Newfoundland, Cape Breton, Nova Scotia,
southern New Brunswick, and the Gaspe Peninsula of Quebec.
The rocks are mostly argillaceous sandstones and shales with
very little admixture of limestone.
The wide-spread continental seas of the Upper Cambrian,
in their latest and most extreme phase, lapped the shores
of the old Pre-cambrian continent from Brockville to the
FIG. 77. SKETCH MAP OF EASTERN CANADA SHOWING THE CHIEF AREAS
OF CAMBRIAN ROCKS
The areas in eastern Quebec may be, in part, Lower Ordovician, and the areas along the
Atlantic coast of Nova Scotia are very uncertain as to age.
vicinity of Ottawa and easterly along the base of the Lauren-
tide mountains. The waves found plenty of prey in the
decayed surface of the old continent for the creation of a
fringe of sandstone along the shore and in the shallow off-
shore waters. This sandstone, known as the Potsdam forma-
tion, is now to be seen along the old shore as indicated above,
and in somewhat wider areas in the extreme western part of
the province of Quebec. The rock is usually a white or
variegated sandstone, composed almost entirely of quartz
grains. While generally too hard for fine carving, the stone
is adapted to building purposes and has been quarried exten-
sively at Smiths Falls, Perth, and in the township of Nepean
in Ontario, also at Beauharnois and other places in Quebec,
THE PALAEOZOIC ERA 189
We have seen that the Pre-cambrian rocks have a very
slight width where they cross the St. Lawrence river at
the Thousand islands. The exposures of Potsdam sandstone
mentioned above are east of the old axis. It is to be expected
that a similar fringe of sandstone would mark the shore of
the old Upper Cambrian sea on the west side also. Doubtless
such a fringe was formed, but its exact location is not ascer-
tainable as it has been buried under later rocks formed in
later seas which advanced farther on the continental axis.
This is a good example of the obliteration of a record by
burial. Nevertheless there is proof of the existence of this
sandstone, as a few small exposures are known at Kingston
Mills and in the township of Loughborough. Also its presence
has been revealed by boring through the overlying rocks at
points farther west.
Following the contact of the Pre-cambrian with later
rocks north and west from the vicinity of Kingston to the
Arctic ocean, we find no more Cambrian rock except near
Sault Ste. Marie. A variegated sandstone, probably of Upper
Cambrian age, forms the "pictured rocks" in Michigan to
the west of the outlet of Lake Superior and crosses the St.
Mary river into Canada at Sault Ste. Marie.
The grandest exposures of Cambrian rocks are found along
the inner ranges of the Rocky mountains. We have seen that
in early Cambrian time a local sinking of the continent per-
mitted the sea to invade this region. The original narrow
depression, the Cordilleran trough, continued through long
geological periods to mark the axis of an area of progressive
submergence. The sediments accumulating in this trough
were gradually bent downward, resulting in the production of
one of the great structural elements of the continent — the
Rocky Mountain geosyncline. Sediments of Lower, Middle,
and Upper Cambrian time accumulated in this depression to
a thickness of 12,200 feet at Mount Robson near the line of
the Grand Trunk Pacific Railway, and in the southern part
of the province of British Columbia to the enormous thickness
of more than 18,500 feet. Many of the grandest peaks of the
Canadian Rockies are composed of Cambrian rocks. The
stupendous changes whereby these sea-made rocks have been
raised to their present lofty position occurred at a much later
igo ELEMENTARY GEOLOGY
date, and constitute one of the most fascinating chapters in
geological history.
The Cambrian rocks of the mountains were originally sand-
stones and shales towards the bottom, with more limestone
at the top. The severe metamorphism which the strata have
undergone has altered the sandstone into quartzite and the
shale into slate; the limestones have been converted, in part
at least, into marble. The cracking and deformation which
these rocks have suffered in the process of mountain-making
have rendered them unfit for structural purposes. Attempts
FIG. 78. LAKE LOUISE, ROCKY MOUNTAINS
have been made to use the slates for roofing without great
success. Lake Louise, one of the beauty spots of the world,
nestles among towering peaks of Cambrian rocks.
THE LIFE OF THE CAMBRIAN
The Proterozoic contains some meagre evidence of the
existence of life, but the fossils are so extremely rare and
so poorly preserved that they are of little or no assist-
ance in working out the geological record. With Cam-
brian time, however, life developed to an extent • that fills
us with astonishment at its complexity and the apparent
abruptness of its appearance.
THE PALAEOZOIC ERA 191
It is a most significant fact that all the branches of in-
vertebrate animals had their inception in or before the Cam-
brian period. Assuming that all life developed from one
original source, we are forced to conclude either that a very
long time intervened between the Pre-cambrian and the
Cambrian or that life existed in the Pre-cambrian to an
extent very much in excess of the evidence that has yet
been found.
We can scarcely conceive of the numerous animals of the
Cambrian having existed without plants for food; never-
theless, the actual evidence of vegetable life is very meagre.
Certain markings and impressions are thought to represent
seaweeds, and in all probability do, but certain evidence of
plant tissue has yet to be found.
While we are impressed by the high development of the
Cambrian invertebrates, two points must be carefully noted:
first, that the total amount of life is very meagre, both in the
number of species and in the actual number of individuals,
compared with the great faunas of succeeding geological
ages; second, despite the high degree of development attained,
the organisms are the most primitive examples known of the
classes to which they belong.
Although it is important to recognise the unexpectedly
high development of Cambrian life on account of its bearing
on the evolution of organisms, we may eliminate most of
the classes in an account of the dominant life of the time.
Most of the groups are so feebly represented that they require
no further mention. The great majority of Cambrian fossils
are either trilobites or brachiopods; the two crustacean
super-orders, ostracods and phyllopods, are also of importance.
TRILOBITES. These animals are crustaceans — i.e. they are
allied to lobsters and crabs, and therefore are to be ranked
high among invertebrate creatures. Trilobites are primitive
crustaceans, however, and differ from all other members of
the class in possessing a longitudinal furrowing of the shell
into three lobes — whence the name tri-lobite. The dorsal
surface is covered by a thin investment which is divided
transversely into three portions — an anterior part, the
head or cephalon; a central part, the body or thorax; and
a posterior part, the tail or pygidium. The cephalon is
192
ELEMENTARY GEOLOGY
composed of three pieces — a central part, and two lateral pieces
known as free cheeks. The line of suture between the parts
is called the facial suture, and is
of the first importance in classi-
fying trilobites.
The thorax is composed of
narrow transverse pieces called
thoracic rings: the number of
these varies greatly in different
genera and is of importance in
classification.
The pygidium is a single piece,
but it shows evidence of having
arisen by the fusion of a number
of original segments.
FIG. 79. A TRILOBITE DISSECTED The under side was protected
TO SHOW CHIEF POINTS OF by a very delicate investment
THE ANATOMY . . r
(«) The head or buckler, consisting of carrying one pair of appendages
the central part (cranidmm) and two to each Original Segment five for
fixed cheeks; (b) The thorax, consist-
ing of a variable number of separate the head, One for each thoracic
"rings"; (c) Ihe tail or pygidium . r i r i
in a single piece. Note the longitudi- Ting, and One IOr each of the
he whole animal. origmal SegmentS of the tail.
Three types of trilobites are recognised according to the
position of the facial suture — a low type in which there is
no suture on the upper surface, an intermediate type in which
ABC
FIG. 80. DIAGRAMS OF THE HEADS OF THE THREE TYPES OF TRILOBITES
(A) Simplest type with no free cheek; (B) Intermediate type with the free cheek including the
posterior angle of head; (c) Highest type in which the free cheek does not include the
posterior angle of the head.
the suture terminates at the back of the head, and a high
type in which it comes out at the side of the head.
Trilobites are characteristic of the whole of the Palaeozoic
era, and were the dominant organisms of the Cambrian period.
The Cambrian trilobites belong to the first two types only;
the higher forms had not yet appeared.
THE PALEOZOIC ERA
193
Fifty-five genera and more than 300 species of Cambrian
trilobites are known: their great diversity is shown by the
remarkable variation in size,
from the little Agnostus, one-
fourth of an inch long with
only two thoracic rings, to
the giant Paradoxides, rang-
ing up to eighteen inches
in length with as many as
twenty thoracic rings. The
three divisions of Cambrian
time are so clearly marked
by different types of trilo-
bites that the Lower Cam-
brian is known as the
Olenellus zone, the Middle
as the Paradoxides zone, and
the Upper as the Olenus
zone.
BRACHIOPODS. In the
Cambrian these creatures
rank in importance next to
the trilobites; they survive
throughout all succeeding ages and exist in the seas of the
present day.
The shell of a brachiopod consists of two halves or valves
which are not alike as in the case of the common clam. On
the other hand, a line drawn from the beak to the front
margin of the shell divides both valves into similar halves;
in this respect, also, the shell of a brachiopod differs from that
of a clam. Brachiopods live with the beak of the shell down-
ward, and are attached to the floor of the sea by a fleshy
structure, the peduncle, which generally comes out between
the two shells. It is customary to draw figures of brachiopods
in the reversed position, i.e. with the beak up.
In the simplest forms the two valves are not connected by
a definite hinge, and the peduncle emerges freely; in higher
forms the valves are hinged and fit closely together, neces-
sitating a special opening for the peduncle. Modifications
of this passage, of increasing complexity, occur with the
FIG. 8l. OLENELLUS, THE TYPICAL
TRILOBITE OF THE LOWER CAM-
BRIAN
From a restoration by Lapworth.
I94
ELEMENTARY GEOLOGY
advance of geological time; as these changes are in accord
both with the march of time and the evolution of the race,
they are used as the main basis for the classification of
brachiopods.
The soft body of the brachiopod lies between the two
valves, to which it is attached by two thin sheets of tissue,
FIG. 82. STRUCTURE OF THE RECENT BRACHIOPOD, MEGALLANIA
FLAVESCENS
I. Interior of the brachial valve showing the loop (S) and muscle scars (a) • 2. Interior of the
pedicle valve showing the muscle scars (p, d), the opening for the passage of the
peduncle (F), and the deltidial plates (D) ; 3. Another species showing the fleshy breath-
ing arms; 4. Vertical section through both valves showing the closing muscles (a), the
opening muscles (c), and the breathing arms. After Davidson.
the mantles. The vital organs are confined to the lower or
beak side of the space between the valves, but the greater
portion of this space is occupied by two plumose "arms,"
which serve as breathing organs and also for conducting
particles of food to the mouth which lies between them. It
was the mistake of regarding these arms as creeping organs
that led to the name "brachiopod/' or "arm-footed."
THE PALEOZOIC ERA
195
In the simpler brachiopods the arms are without a hard
shelly support, but in the higher forms calcareous structures
are developed in one valve to give rigidity to the arms. These
supports may be simple spurs or spirally coiled threads, or
loop-like structures. The characteristics of these arm-supports
are of great importance in classification, second only to the
structure of the opening for the peduncle.
Forty-four genera and 477 species of Cambrian brachiopods
have been described. It is significant that of these 229
species belong to the lowest order, in which the peduncle
emerges freely between the valves and there is no hinge, and
that 1 88 species belong to a higher order, still without hinge,
FIG. 83. FOUR TYPES OF BRACHIOPODS
i. Simplest type without hinges; 2. Type with hinge, but without calcareous support for
breathing arms ; 3. Type with spiral supports; 4. Type with looped supports. Figures:
and 2 show vascular markings and muscle scars.
but with a slight modification in the peduncular opening.
The remaining no species have a simple hinge, but there are
no representatives of the higher orders with calcareous
supports for the arms and complex peduncular passages.
OSTRACODS. Ostracods are small crustaceans enclosed in
a bivalved shell. In the fossil condition only the shells are
known : these resemble very closely a half-bean, but they are
usually of smaller size than the average bean. The outline
varies with the different genera, and details of surface orna-
mentation are of value in determining species. The Cambrian
rocks of the maritime provinces of Canada alone have yielded
about forty species of ostracods.
PHYLLOPODS. Like trilobites and ostracods, these organisms
are crustaceans; they are closely related to the ostracods,
but the shell is not in two pieces and it does not cover
196 ELEMENTARY GEOLOGY
the whole of the body. Some very interesting forms have
been obtained from the Cambrian rocks of British Columbia.
Despite the great age and serious metamorphism of most
Cambrian strata, some few favoured localities have yielded
fossils in an exquisite state of preservation. Not only are the
hard parts preserved, but impressions of soft tissue are found,
and indications of such delicate organs as the antennae and
limbs of crustaceans. The most remarkable of these rare and
beautifully preserved fossils were obtained by Dr. Walcott
from shales of Middle Cambrian age near Burgess pass,
British Columbia. They include jelly-fish, sea-cucumbers,
worms, and some of the higher arthropods with the various
organs delicately preserved.
It will be noticed that in the above account only the life
of the sea has been mentioned. We know nothing of the
continent which doubtless made up most of Canada in
Cambrian time, except that it had a weathering rock surface
from which rivers brought down mud and sand. Probably it
was bare of plant life — a desert — because land plants had not
yet come into being. Without land vegetation, one may
suppose an equal lack of air-breathing animals. The continent
was seemingly a lifeless wilderness.
CAMBRIAN FOSSILS OF THE MARITIME PROVINCES
The fossils of this region are distinctly of an Atlantic type
and show relationships to European species. The commonest
fossils are trilobites ; brachiopods are less numerous ; ostracods
and other types occupy third place. Common examples are:
Trilobites:
Paradoxides eteminicus, Conocoryphe baileyi, Microdiscus
regulus.
Brachiopods :
Protorthis billingsi, Lingulella gregwa.
FOSSILS OF THE POTSDAM SANDSTONE
The Potsdam sandstone of Ontario and Quebec shows few
fossils. The one really characteristic species is Lingulella
acuminata. Worm burrows and the tracks of unknown
organisms have been found.
FIG. 84. CAMBRIAN FOSSILS OF BRITISH COLUMBIA
Trilobites: i. Ogygopsis klotzi; 2. Neolenus serratus; 3. Agnostus montis; 4. Ptychoparia
cordillerce. Phyllopod: 5. Anomalocaris canadensis. Brachiopods: 6. Micromitra
pannula, ventral and side views; 7. Obolus mcconnelli, pedicle and brachial views-
8. Acrotreta depressa, pedicle and lateral views. Nos. i, 2, 4 and 5 natural size, the other
figures greatly enlarged. After Walcott.
198 ELEMENTARY GEOLOGY
CAMBRIAN FOSSILS OF THE ROCKY MOUNTAIN REGION
The Cambrian rocks of this region are not rich in fossils
throughout, but in places the characteristic species of Lower,
Middle and Upper Cambrian are found in abundance and in
an excellent state of preservation. The fauna is distinctly of
a Pacific type, and while generally similar, it differs from that
of the eastern region in detail: for instance, the typical
Paradoxides is absent from the middle division, but its place
is taken by related genera.
The Middle Cambrian is much the richest in fossils; the
following characteristic examples are all from that horizon :
Trilobites :
Ogygopsis klotzi, Neolenus sermtus, Ptychoparia cordillerce,
Agnostus montis.
Brachiopods :
Obolus mcconnelli, Micromitra pannula, Acrotreta depressa.
Phyllopod:
Anomalocaris canadensis.
CHAPTER VI
THE ORDOVICIAN PERIOD
CAMBRIAN time was followed by a long period to which the
name Ordovician has been given, as the rocks of this system
were first studied in Wales, a part of which was inhabited in
Roman times by a tribe called the Ordovices.
PHYSICAL EVENTS OF THE ORDOVICIAN IN
NORTH AMERICA
We have seen that the later stages of Cambrian time were
marked by a great advance of the sea on the continent. The
close of the Cambrian and the beginning of the Ordovician
seem to indicate a general withdrawal of the water from the
present land areas. The conditions are not well understood
for the whole continent, but it is known that a gradually
receding sea occupied the country from eastern Ontario
south and east through parts of the maritime provinces
and the eastern United States to the Atlantic ocean. At the
same time a pronounced submergence occurred in Nevada
and Utah. This period of emergence and of deposition in
rather confined areas represents the Lower Ordovician or
Canadian time.
Now followed a downwarping of the eastern interior of the
continent whereby seas, not in connection with the Atlantic
ocean, covered large areas in the eastern United States and
the southern part of eastern Canada. It is believed that this
submergence finally became so pronounced that a broad con-
nection was established across the highlands of Canada with
the waters of the Arctic ocean. Many oscillations of land and
water occurred during this time, which is known as the Middle
Ordovician, and is sometimes erroneously called Champlainian.
The Middle Ordovician seas having largely withdrawn, a
new invasion of waters spread over the continent from the
Gulf of Mexico northward and eventually became united with
199
200
ELEMENTARY GEOLOGY
a great flood advancing southward from the Arctic ocean.
This epoch is the Upper Ordovician, and is called Cincinnatian
by American geologists.
The physical conditions in the Cordilleran region are not so
well understood, but the Rocky Mountain geosyncline con-
tinued to be an area of depression, with the result that
FIG. 85. PAL^EOGEOGRAPHIC MAP OF NORTH AMERICA IN UPPER
ORDOVICIAN TIME
White areas, land; vertically linel areas, water in early Richmond time; horizontally lined
areas, water in middle Richmond time. From Pirrson and Schuchert, " Textbook of Geology "
Ordovician strata were deposited on top of the great accumula-
tions of Cambrian sediments.
The close of Ordovician time was marked by a dis-
turbance of the continent in the Atlantic border region.
This or later disturbances seriously affected the Ordovician
strata of the maritime provinces, throwing them into folds
and greatly altering their original physical characteristics.
As the Green mountains of Vermont and their southern
THE ORDOVICIAN PERIOD 201
extension, the Taconic range, were first uplifted at this time,
the event has been called the Green Mountain or Taconic
revolution.^ It is to be noted, however, that the Ordovician
rocks of the interior of the continent show scarcely any effect
of this upheaval of the region along the Atlantic coast.
The Ordovician as a whole was a period of limestone forma-
tion, although shales form a prominent element in the strata
of certain localities. On the other hand, sandstones occur to
a very limited extent. The movements of land and water
were on a grand scale in Ordovician time ; the formations are
heavier and of greater geographical extent than is usual in
any later systems.
THE ORDOVICIAN SYSTEM IN CANADA
The Canadian occurrences of Ordovician strata may be
grouped in areas as follows:
i. ACADIAN AREA. If a line be drawn along the axis of
Lake Champlain, thence north to the St. Lawrence river, and
down the river to the ocean, it will cut off from the rest of
Canada an area which has been greatly disturbed, not only
by the Taconic revolution above referred to, but by subse-
quent earth movements of great magnitude. This line marks
the location of a great fault — the Champlain fault — as the
strata on the two sides have been thrown hundreds of feet out
of accord. The Ordovician rocks to the east of the fault have
been so upturned and metamorphosed, and the characteristic
fossils so destroyed, that their study is attended with diffi-
culties far exceeding those of the other Ordovician regions
of Canada. Strata of this age occur in belts of limited extent
with a general north-east and south-west trend ; the chief of
these are as follows:
(a) The eastern townships of Quebec.
(b) The south-eastern part of the Peninsula of Gaspe.
(c) Central New Brunswick from Chaleur bay south-
westward across the province.
(d) Northern Nova Scotia from Minas basin to the
eastern point of the mainland.
1 In the light of recent investigations this event scarcely deserves
the name " revolution." It was formerly regarded as of great magnitude.
202
ELEMENTARY GEOLOGY
2. ANTICOSTI ISLAND. The northern coast of the island of
Anticosti is occupied by Ordovician rocks which are un-
disturbed, as the island lies north of the Champlain fault.
Well-preserved fossils may be obtained in abundance from
the exposures along this coast.
3. ST. LAWRENCE AREA. Eastern Ontario and western
Quebec, from the Potsdam sandstone area to the Champlain
fault and along the north shore of the St. Lawrence river to
a short distance below the city of Quebec.
4. ONTARIO AREA. Ordovician rocks cross the province
of Ontario in a broad belt extending from Lake Ontario
to Georgian bay, and reappearing on the north shore of
Manitoulin island and on the islands between Manitoulin
and the mainland. The belt is widest in the south, form-
ing the shore of Lake Ontario from Kingston to beyond
Toronto; on Georgian bay it reaches from Matchedash
bay to Owen sound.
A great system like the Ordovician is naturally divisible
into series, and the series into formations. While the series
may be recognised the world over, the lesser divisions, forma-
tions, are necessarily of limited extent. As an example of the
subdivision and classification of the rocks of the Ordovician
system, those occurring in Ontario are arranged as follows:
THE SEQUENCE OF ORDOVICIAN ROCKS IN ONTARIO
SYSTEM
SERIES
FORMATION
Ordovician
Upper Ordovician or
Cincinnatian
Richmond
Lorraine
Utica
Middle Ordovician or
" Champlainian "
Collingwood 4
Trenton
Black River
Lowville
Pamelia
Aylmer (Chazy)
Lower Ordovician or
Canadian
Theresa (Beekmantown)
These formations consist of rock differing in composition
and appearance, but not always sufficiently so to enable one
THE ORDOVICIAN PERIOD
203
to state the formation from which a given sample has been
taken. As each formation, however, has its own distinctive
fossils, an examination of these affords certain evidence as to
the age of the rock.
In the area under consideration successively higher forma-
tions are encountered as one goes westward from the Pre-
cambrian axis. Naturally, on the east side of the axis the
younger formations are encountered as one advances east-
ward. The formation at Kingston is Black River, and at
Toronto, Lorraine.
FIG. 86. SKETCH MAP OF EASTERN CANADA SHOWING IN BLACK THE
CHIEF AREAS OF ORDOVICIAN ROCKS
Small areas also occur in Nova Scotia, and the area in New Brunswick dotted in Fig. 102 is
in part Ordovician.
5. HUDSON BAY AREA. Ordovician rocks occupy a con-
siderable area to the west of Port Nelson and Fort Churchill
on the west side of Hudson bay.
6. ARCTIC ISLANDS AREA.
7. MANITOBA AREA. Ordovician rocks, with a width of
about 100 miles, extend from the international boundary
northward along the flank of the Pre-cambrian axis to
Latitude 56° N.
8. ROCKY MOUNTAIN AREA. Ordovician rocks overlie the
Cambrian strata in the middle ranges of the Rocky mountains.
204 ELEMENTARY GEOLOGY
ECONOMIC PRODUCTS OF ORDOVICIAN ROCKS
The limestones of the Ordovician system are extensively
quarried for building, for lime and cement-making, for con-
crete, and for macadam. Large quarries are operated in Middle
Ordovician strata at Hull, Ottawa, Montreal, Quebec, King-
ston, Longford Mills, and other places. The bituminous shales
of the Collingwood and Utica formations were distilled for oil
before the discovery of petroleum, and may again be required
for this purpose.
Middle Ordovician rocks yield excellent building-stone at
Tyndall, Manitoba, and the upper division has been quarried
at Stony mountain and elsewhere in Manitoba for crushed
rock and lime-making.
Marble is obtained from Ordovician rocks in the meta-
morphic area of the eastern townships of Quebec.
The natural gas of central Ohio and of the Leamington and
Norfolk and Elgin county fields in Ontario is derived from
strata of this age by boring through the overlying rocks.
Most of the celebrated mineral waters of Ontario and
Quebec issue from Ordovician rocks, more particularly in the
St. Lawrence area.
LIFE OF THE ORDOVICIAN
Compared with that of the Cambrian, the life of the Ordo-
vician is more varied and much more abundant; it has been
called the "first great fauna." The predominance of limestone
attests the great amount of life, as many of these rocks are
visibly composed of the remains of shelled organisms.
ORDOVICIAN PLANTS
Ordovician plants are known by distinct impressions which
leave no doubt as to their origin from seaweeds which were
entombed on the floor of the sea. Terrestrial plants are
unknown.
ORDOVICIAN INVERTEBRATES
Plant remains being meagre and vertebrates almost entirely
absent, the Ordovician life was essentially one of inverte-
THE ORDOVICIAN PERIOD
205
brates. As the time was very long and many changes took
place, it is somewhat difficult to speak of the life as a whole ;
this difficulty is increased by the fact that no classes and few
orders are absolutely confined to the period. On the other
hand, certain groups of organisms reached their maximum
development; these are to be regarded as particularly char-
acteristic, but they do not by any means represent the
whole life. These outstanding groups are brachiopods,
trilobites, graptolites, cystids, receptaculites, and possibly
bryozoans. A brief account of the life of the time follows.
SPONGES. Many sponges occur, particularly in the lower
FIG. 87. ORDOVICIAN CORALS
i. Columnaria halli 2. Streptelasma corniculum. After Billings and Lambe.
part of the system; in Canada, however, examples of this
kind of creature are rare.
RECEPTACULITES. These very characteristic Ordovician
creatures are of doubtful zoological position, but are probably
allied to the sponges. They build hollow, vase-shaped skeletons
of considerable size — up to a foot in diameter. The wall is
composed of an inner and an outer layer connected by pillars.
The fossils are easily recognised, even in fragments, by the
peculiar curved, radial arrangement of the pillars, which is
reflected on both the inner and outer wall. Beautifully silici-
fied specimens are common at Paquette's rapids in Ontario,
and very large examples are frequent in the Ordovician
rocks of Manitoba.
CORALS. Corals are small soft-bodied animals in which a
206
ELEMENTARY GEOLOGY
single body cavity performs all the vital functions, i.e. there
is no intestine or circulatory system. Corals may live singly
or in colonies; in either case they secrete a skeleton of car-
bonate of lime which is correspondingly single or compound.
Streptelasma is a common example of single Ordovician corals,
and Columnar ia of the compound type. While corals are more
abundant than in the Cambrian, they do not reach the im-
portant position which they fill in later geological periods.
GRAPTOLITES. Hydrozoa are coelenterate animals like
corals, but of simpler organisation and smaller size. Grap-
tolites are thought to be hydrozoans which build compound
skeletons of horny matter instead of lime. In the fossil
FIG.
ORDOVICIAN GRAPTOLITES
i. Phyllograptus angustifolius; 2. Climacograptus typicalis; 3. Diplograftus foliaceus.
Natural size. After Hall and Ruedemann.
condition, the skeletons of graptolites have been reduced to
graphite and appear like pencil marks on slabs of rock. In
life the colonies were free and drifted with the currents of the
ocean. This habit, together with the fact that they are short-
range forms, makes them very valuable for the determination
of the different formations. These organisms are among the
most characteristic of Ordovician fossils. Diplograptus and
Monograptus are typical simple forms, while Phyllograptus
and Tetragraptus exemplify the more complex kinds.
ECHINODERMS. These organisms, as the name implies, are
characterised by the possession of a hard outer crust or shell
composed of plates or rods of carbonate of lime. There are
two rather distinct types of echinoderms — those that are
fastened by a stalk to the sea floor, such as the existing sea
THE ORDOVICIAN PERIOD
207
lilies, and those which are capable of locomotion, like the star-
fishes and sea-urchins of to-day.
In the Ordovician, sea-urchins are unknown and star-fish
are represented by rare examples only. The fixed or stalked
FIG. 89. ORDOVICIAN CRINOIDS AND CYSTIDS
i. Cupulocrinus humilis; 2. Ottawacrinus typus; 3. Pleurocystis squamosus; 4. Reteocrinus
\alveolatus; 5. locrinus subcrassus ; 6. Glyptocrinusdecadactylus; 7. Malocystismurchisoni.
All figures natural size. After Springer and Hall, and from original photographs.
type, however, is common; of these, two different kinds are
found, known as cystids, and crinoids or sea lilies.
' Cystids are stalked echinoderms of simple organisation and
without a circlet of waving arms at the top ; they are the sim-
plest of all echinoderms, and reached their maximum develop-
ment in the Ordovician. Malocystis and Pleurocystis are the
commonest genera in the Ordovician rocks of eastern Canada.
208 ELEMENTARY GEOLOGY
Crinoids, or sea lilies, resemble cystids in the possession of a
jointed column or stem and a plated cup or body; they
differ, however, by having a circlet of waving arms above
the cup. The popular name " sea lily " is given on account
of the general resemblance to a lily, not because crinoids are
plants or in any way related thereto.
Crinoids were so abundant in the Ordovician that, in certain
places, whole layers of rock are made up of the disassociated
plates. Owing to the disintegration of the remains after
death, entire specimens are found only in favoured localities.
The Middle Ordovician rocks at Kirkfield, Ontario, have
yielded a remarkable assemblage of crinoids, and the strata
of the upper division at Toronto are in places filled with
columns although whole specimens are rare. Common genera
are Archaocrinus, Glyptocrinus, Heterocrinus, Cupulocrinus,
and Dendrocrinus.
Although crinoids were numerous in the Ordovician, they
attained a much greater development later; they are not so
typical of the Ordovician as are the cystids.
BRACHIOPODS. These organisms attained a remarkable
development, reaching, if not their maximum, a position only
equalled by that of the next great system. The thin-shelled
hingeless types, so characteristic of the Cambrian, are less
in evidence, their place being taken by hinged forms which,
however, are without a calcareous support for the arms. The
highest type has not yet made its appearance in force.
Common genera of the Canadian Ordovician rocks are Hebert-
ella, Rafinesquina, Dalmanella, Plectambonites, Zygospira,
Dinorthis, and Platystrophia. Plectambonites sericeus is so
common both in the middle and upper divisions that
thick layers of limestone are composed almost entirely of
its remains.
BRYOZOA. These organisms, almost unknown in the Cam-
brian, appear with extraordinary profusion in the Ordovician,
and maintain a position of great importance throughout the
whole of the Palaeozoic era. By reason of their great numbers
and wide distribution, and the limited range in time of
individual species, bryozoans are of the highest value in
determining the formations of the Ordovician and later
Palaeozoic systems. On the other hand, their study is attended
FIG. go. ORDOVICIAN BRACHIOPODS
i. Rafinesquina alternata, brachial and pedicle views; 2. Dalmanella testudinaria, brachial
and side views; 3. Orthis tricenaria, brachial and side views; 4. Zygospira recuruirostris;
. 5. Dinorthis pectinella, pedicle and lateral views; 6. Catazvga headi, brachial and lateral
views; 7. Zygospira modesta, brachial and pedicle views; 8. Rhynchotrema capax, lateral
and pedicle views; 9. Plectambonites sericeus, external of brachial and internal of
pedicle valves; 10. Camerella volborthi, brachial and pedicle views; n. Dinorthis
subquadrata; 12. Hebertella borealis, pedicle and lateral views ; 13. Hebertella imperator,
pedicle view. All figures natural size. After Billings and others.
210
ELEMENTARY GEOLOGY
with many difficulties which detract from their value in the
hands of the amateur.
Bryozoans are extremely small, sack-shaped animals with
a simple coiled intestine and a circlet of waving arms around
the mouth. They live in colonies and build a compound
skeleton resembling that of a compound coral. The bryozoan
skeleton, however, is very much finer, as the little individuals
are seldom of greater diameter than a needle. The skeleton
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'^WteftS'® A/&l;>-i
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FIG. 91. STRUCTURE OF LONG-CELLED OR TUBULAR BRYOZOANS
i. Portion of a branching colony, natural size; 2. Surface enlarged showing the openings
of the tubes; 3. Tangential section, showing the tubes in cross section and the small
hard nodes (acanthopores) ; 4. The same greatly enlarged; 5. Vertical section, showing
the tubes and the cross partitions (diaphragms). After Nicholson.
of a typical Ordovician bryozoan may be sub-globular, hemi-
spheric, cake-shaped, branching like a tree, or forming a
crust over other objects. By the naked eye the average
bryozoan would scarcely be recognised as a fossil. If the
surface be examined with a lens, it is seen to be covered with
small pits; these pits are the openings of the cells in which
the individual creatures lived. If the fossil be broken across,
the fractured surface presents a fibrous appearance; the
fibres are really little tubes closely set together. Each tube
represents the cavity in which a bryozoan lived, and the pits
THE ORDOVICIAN PERIOD
211
on the surface are the openings of these tubes. All bryozoans
do not show this tubular structure, but the great majority of
Ordovician bryozoans do. Common genera are Prasopora,
Monticulipora, Dekayella, Batostoma, and Hallopora.
GASTROPODS. These organisms, the belly-footed molluscs,
secrete a single-valved spiral or saucer-shaped shell which
is borne on a hump at the posterior part of the body. The
familiar garden snail .will serve as an example of the class.
Gastropods of a simple kind are quite abundant in certain
FIG. 92. ORDOVICIAN OSTRACODS AND BRYOZOANS
Ostracoda: i. Beyrichia tuberculata; 2. Leperditia hisingeri. Bryozoa: 3. Hallopora dahi;
4. Bythopora delicatula; 5. Dekalella ulrichi; 6. Prasopora selwyni.
strata of the Ordovician, but they do not attain the important
position which they fill at a later time.
Typical Ordovician gastropods, each representing a differ-
ent type, are Hormotoma, Raphistomina, Bellerophon, and
Maclurea. The latter genus is particularly characteristic of
the period.
PELECYPODS. The bivalved molluscs, of which the common
clam is a typical example, are called pelecypods because they
have a hatchet-shaped foot or creeping organ. These creatures
form the great bulk of the shell-fish of the present day, and
they existed in vast numbers throughout the geological ages.
Almost unknown in Cambrian time, they are represented in
the Ordovician by thin-shelled, primitive types which are
212
ELEMENTARY GEOLOGY
without the complicated hinge apparatus characteristic of
modern forms.
Pelecypods are rare in Lower Ordovician rocks. Cyrtodonta
and Ctenodonta are common Middle Ordovician genera. More
FIG. 93. ORDOVTCIAN GASTROPODS
i. Hormotoma anna (Beekmantown) ; 2. Hormotomatrentonensis (Trenton); 3. Raphistomina
canadensis (Beekmantown) ; 4. Maclurea logani (Black River) ; 5. Liospira vitruvia
(Trenton); 6. Sinuites cancellatus (Trenton). All figures natural size.
numerous species occur in the upper division, and they
may be secured in abundance from the strata exposed near
Toronto. Particularly numerous are Modiolopsis, Bysso-
nychia, and Pterinea.
CEPHALOPODS. These are the largest, the most highly
specialised, and the strongest and most predaceous of the
molluscs. The class includes such forms as the squids, cuttle-
THE ORDOVICIAN PERIOD
213
fish, and pearly nautilus. The latter organism is closely related
to the type of cephalopod which existed in Palaeozoic time, and
may be described as typical of the class.
FIG. 94. ORDOVICIAN PELECYPODS
i. Byssonychia radiata (Lorraine); 2\ Pterinea demissa (Lorraine) ;* 3. Ctenodonta nasuta
(Black River). All figures about seven-eighths natural size.
The shell of the pearly nautilus, which sometimes attains
a diameter of a foot or more, is like a gradually tapering cone
FIG. 95. ORDOVICIAN PELECYPOD
Modiolopsis modiolaris in Lorraine shale.
which has been coiled symmetrically in one plane. The interior
is divided into compartments by transverse partitions, known
as septa, which are connected with one another by a small
2I4
ELEMENTARY GEOLOGY
tube called the siphuncle. The animal lives in the outermost
compartment; the inner compartments are empty, and
probably serve as an apparatus
to keep the creature at fixed
depths in the water. The outer
layer of the shell shows broad
transverse strips of white and
brown. When this layer is
removed the shell presents a
beautiful pearly surface, whence
the name "pearly nautilus."
Cephalopods of this type are
called Nautiloids.
In the Ordovician, Creatures
the pearly nautilus
r j
abounded. Many of them
. . rr , . •'.--«
differed, however, in having
straight instead of coiled shells ; they are known as Orthoceras
in consequence. A straight form with a rapidly tapering cone,
Gonioceras, is very characteristic of the Middle Ordovician
FIG. 96. NAUTILUS POMPILIUS, A
RECENT NAUTILOID, WITH THE
SHELL REMOVED ON ONE SIDE
(a) The mantle enclosing the body and
passing backwards as a narrow tube, the verV
siphon; (b) Dorsal lobe of mantle; (c) *
hood; (d) Funnel; (h) Muscle; (o) Eye.
After Owen.
FIG. 97. ORDOVICIAN NAUTILOIDS
i. Plectoceras halli, 2. Trocholites ammonius; 3. Gonioceras. From specimens and from
" Lethcea Geognostica."
time; Endoceras is a type of large size with a relatively big
siphuncle; Trocholites and Eurystomites are coiled forms.
Actinoceras crebriseptum is one ef the commonest and most
striking fossils found in the rocks near Toronto.
THE ORDOVICIAN PERIOD
215
TRILOBITES. Trilobites reached their maximum develop-
ment in the Ordovician. All the Cambrian species and most
FIG. 98. ACTINOCERAS CREBRISEPTUM FROM THE LORRAINE ROCKS AT
TORONTO
The bottom specimen has the outer shell removed, exposing the edges of the septa; the
top specimen is half worn away, showing the septa and the siphuncle.
j- FIG. 99. ORDOVICIAN TRILOBITES
i. Ogygites canadensis (Collingwood) ; 2. Cryptolithus tesselatus (Trenton to Lorraine) ;
3. Triarthrus spinosus (Utica and Collingwood); 4. Ceraurus pleurexanthemus. All
figures about natural size.
of the genera have become extinct, their place being taken by
new races which belong, for the most part, to the intermediate
216
ELEMENTARY GEOLOGY
type, although a few of the lowest type survive and a few of
the highest type are introduced. Common genera are Isotelus,
Calymene, Trinucleus, Triarthrus, and Cheirurus.
OSTRACODS. The remains of the small shells of these crea-
tures are abundant in the Ordovician rocks of certain localities.
FIG. IOO. ORDOVICIAN TRILOBITES
i. Isotelus maximus (Lorraine) ; 2. Calymene senaria (Trenton) ; 3. Isotelus gigas (Trenton).
Leperditia canadensis is very common, and may be collected
in extraordinary numbers from the exposures near L'Original
in Ontario.
VERTEBRATES. Animals with backbones have not been
found in the Ordovician rocks of Canada, but fragmentary
remains of a few primitive fish have been discovered in
Colorado, Wyoming, and South Dakota.
CHAPTER VII
THE SILURIAN PERIOD
THIS period, like the two preceding, derives its name from the
locality in which it was first studied — in this case, the south
part of Wales and the adjoining portions of England, which
region was formerly inhabited by a tribe of Britons known
as "Silures."
PHYSICAL EVENTS OF THE SILURIAN IN
NORTH AMERICA
We have seen that the Ordovician was brought to a close
by a physical disturbance, called the Taconic revolution,
which to some extent displaced the rocks of earlier time so
that the Silurian strata rest upon them with more or less
unconformity throughout the Appalachian region of the
United States and the maritime provinces of Canada. In
the continental interior the disturbance was much less
extensive, as the Silurian rocks are separated from the
earlier strata by only a slight disconformity which in
places is scarcely perceptible.
While Ordovician time is marked by great continental
elevations and depressions, with wide-spread seas and con-
sequent extended formations, the Silurian as a whole witnessed
only one great depression with many minor oscillations. The
formations of the Silurian seas, therefore, are more local and
of less extent than those of the Ordovician.
The initial submergence of the period seems to have affected
the Acadian region, for the lowest strata are found in Nova
Scotia and Anticosti island. Before the close of Lower Silurian
time, the seas had invaded the interior of the continent and
the middle division of the period witnessed the maximum
expansion, with waters covering a large part of the continent,
which, however, presented the appearance of a vast archi-
pelago. Upper Silurian time was largely an epoch of emergence,
with the marine waters gradually withdrawing from the
interior region and later from the Arctic area of submergence.
217
218
ELEMENTARY GEOLOGY
THE SILURIAN SYSTEM IN CANADA
The exposures of Silurian rocks in Canada may be grouped
in areas as below:
1. ACADIAN AREA. Silurian rocks occur as narrow north-
east and south-west strips in Newfoundland and Nova Scotia ;
they form the south side of the island of Anticosti, and occur
over a wide area in the northern part of New Brunswick
and adjacent portions of Quebec. The rocks are mostly
black, red and green shales, with argillaceous limestones
and some sandstone.
2. ONTARIO AREA. Strata of this period form a wide belt
crossing the .province of Ontario from the Niagara river to
Manitoulin island. The lower rocks are sandstones and
shales, but with the deepening seas of the Middle Silurian
these gave place to heavy dolomites, which were again followed
by shales in the closing stages of the period.
As in the case of the Ordovician, this area will be used to
exemplify the subdivision of the Silurian system into series
and formations.
THE SEQUENCE OF SILURIAN ROCKS IN ONTARIO
SYSTEM
SERIES FORMATION
Silurian
Upper Silurian or
Cayugan
Monroe and Bertie
Salina
Middle Silurian or
Niagaran
Guelph
Lockport
Rochester
Clinton
Lower Silurian or
Oswegan
Medina
Cataract
The Cataract, Medina, Clinton, and Rochester are composed
chiefly of sandstones and shales. All these rocks are of a soft
nature, but the overlying Lockport is a heavy dolomitic
limestone deposited in the Middle Silurian sea at the time of
its greatest extension and deepest water. In consequence
of the occurrence of this hard, heavy stone above the
THE SILURIAN PERIOD
219
soft underlying formations, a striking feature in the topo-
graphy of the province has arisen. Millions of years have
intervened between the time that these rocks were lifted
out of the sea and the present. During all this time the
forces of erosion have been at work, with the result that
the softer rocks have been worn away except where the
hard Lockport dolomitic limestone has afforded them protec-
tion. The line to which the erosion has advanced westward
is marked, therefore, by a steep cliff or escarpment (cuesta)
which reaches from Queenston heights to Manitoulin island,
FIG. 101. THE NIAGARA CUESTA
except where it is interrupted by the waters of Lake Huron.
The province is divided, therefore, into two topographic units
—the western upland and the eastern lowland, separated by
the significant escarpment which is known to the inhabitants
of the region as the Hamilton Mountain. Niagara Falls owes
its existence to the same set of causes; for had there been
no escarpment there would be no falls, and no escarpment
would have been formed had the arrangement of hard and
soft rocks been different. To the sequence of events in the
far-distant Silurian sea we owe the present configuration of
the province and the possession of one of the scenic wonders
of the world.
From the above remarks it is apparent that the soft lower
220
ELEMENTARY GEOLOGY
rocks have been washed away except where they are covered
by the Lockport stone; in consequence, these formations
have little or no lateral extent and are to be seen only in
the face of the cliff. Splendid opportunities for their study,
however, are afforded in the gorge of the Niaraga river and
along the face of the escarpment from Queenston heights
to Manitoulin island.
3. HUDSON BAY AREA. Silurian rocks form the west coast
of Hudson bay from the mouth of the Ekwan river to Cape
Churchill.
4. MANITOBA AREA. A belt of Silurian rocks occupies
FIG. IO2. SKETCH MAP OF^EASTERN.. CANADA SHOWING IN BLACK THE
CHIEF AREAS OF SILURIAN ROCKS
The dotted area is chiefly Silurian, but includes some Devonian towards the north and some
Ordovician towards the south. Small areas of Silurian rocks also occur in Nova Scotia.
the country between Lake Winnipeg and Lakes Manitoba
and Winnipegosis. The rocks are whitish, yellowish, and
cavernous dolomites, passing into yellowish and reddish
calcareous shales.
5. ROCKY MOUNTAIN AREA. Silurian strata overlie the
Ordovician beds in the eastern ranges of the Rocky mountains.
On the Canadian Pacific Railway dolomitic limestones and
white quartzites occur to a thickness of 1850 feet. The belt
seems to widen toward the north and to reach into Alaska.
ECONOMIC PRODUCTS OF SILURIAN ROCKS
The Silurian strata of the Acadian region contain no
deposits of economic importance. Their original composition
THE SILURIAN PERIOD
221
and the results of subsequent deformation have rendered
them unfit for building purposes.
In Ontario sandstones are quarried from the Cataract
formation at a number of points along the face of the Niagara
cuesta, particularly at the forks of the Credit river, north of
Toronto. This stone, both grey and brown, has been used
extensively in Toronto and other places in western Ontario.
The heavy limestones and dolomites of the Lockport and
Guelph formations are used for building and lime-making at
FIG. 103. SKETCH MAP OF CENTRAL CANADA SHOWING THE
AREAS COVERED BY PALAEOZOIC ROCKS
Ordovician, black; Silurian, dotted; Devonian, black with white dots.
Queenston, Hamilton, Guelph, Owen Sound, and Wiarton.
Hard cherty layers of the Lockport formation yield an excel-
lent material for road-making, and the Silurian rocks of
Manitoba are employed for crushed stone.
The shallowing seas and desert climate of later Silurian
time permitted the evaporation of sea water, with the con-
sequent deposition of beds of gypsum and salt. Gypsum is
extensively quarried from these strata at Paris and Caledonia
in Ontario, and near Gypsumville in northern Manitoba. Salt
is produced in large amount from the Silurian rocks of western
Ontario, particularly near Windsor. Deep holes are bored
through the overlying rocks into the salt-bearing strata.
222
ELEMENTARY GEOLOGY
Water is allowed to pass down the bore-holes, and the resulting
brine is pumped up and evaporated.
CORRELATION OF SILURIAN FORMATIONS
The formations of the Silurian system in Ontario have been
given in some detail ; the rocks of the other areas are similarly
divided into formations, but these formations are not the
same, and they do not bear the same names. Nevertheless,
the formations of the Silurian or of any other system, in
any part of the world, may be compared with one another.
Such comparisons are usually called correlations, and they
are expressed by means of correlation tables.
The following table is introduced as an example; it shows
the correlation of the Silurian rocks of Arisaig, Nova Scotia,
as determined by Williams, with those of Ontario and of
England.
CORRELATION TABLE OF THE SILURIAN FORMATIONS
OF NOVA SCOTIA, ONTARIO, AND ENGLAND
SYSTEM
FORMATION
Silurian
Nova Scotia
Ontario
England
Stonehouse
Moydart
McAdam
Ross Brook
Beech-hill Cove
Ludlow (part)
Wenlock
Upper Llandovery
Lower Llandovery
Lower Llandovery
Lockport
Rochester
Clinton
Medina and Cataract
LIFE OF THE SILURIAN
In many respects the general life of this period is similar to
that of the Ordovician. Trilobites, brachiopods, cephalopods,
and bryozoans still abound ; graptolites and cystids, however,
show a marked decline ; sponges, corals, and crinoids occur in
greater profusion than before. A new type of life, the euryp-
terids, disputes the supremacy of the seas with the trilobites;
fishes occur in some abundance; and the first terrestrial
plants make their appearance.
While the Silurian life of the whole world is similar, it is by
THE SILURIAN PERIOD
223
no means identical in the different continents. Even in North
America the life differs in the different basins of deposition.
The fossils of the Acadian area resemble those of Ontario, but
only a few species are identical. The Silurian fossils from the
Hudson Bay and Manitoba areas differ from those of Ontario
FIG. 104. SILURIAN CORALS
i. Strombodes pentagonus ; 2. Favosites favosus ; 3. Diphyphyllum multicaule ; 4. Omphyma
verrucosa ; 5. Halysites catenulatus ; 6. Halysites catenulatus, seen from above. All figures,
except No. 5, are slightly under half size, and represent specimens from Manitoulin island.
and show a closer relationship to European forms, indicating
a migration through Arctic regions. The fossils of the Silurian
rocks of the Rocky Mountain area are not numerous: they
indicate a fauna derived from Pacific waters.
An outline of the life of Silurian time follows :
PLANTS. In the lower part of the Silurian, as in the Ordo-
vician, no vegetable life of higher organisation than seaweeds
224
ELEMENTARY GEOLOGY
has been found; in the upper part, however, occurs the
earliest known terrestrial plant, Psilophyton, a very primitive
spore-bearing plant discovered by Dr. Dawson in the Silurian
rocks of Gaspe.
SPONGES. In Middle Silurian time a type of sponge with
very thick walls composed of interlocking spicules of silica
makes its appearance in some numbers. On account of the
rigid character of the skeleton, these sponges are known
as "stony" or "lithistid" sponges: they may be procured
in abundance from the cherty layers at the top of the
"mountain" at Hamilton, Ontario.
CORALS. Corals are much more abundant than in the
Ordovician; in Middle Silurian time they formed great reefs.
Fossil hill in Manitoulin island is a famous collecting-ground
for these Silurian corals. The remains are enclosed in lime-
stone, but have been converted into silica and weather out on
the surface on account of their superior hardness. Common
genera are, Haly sites (chain coral), Favosites (honey-comb
coral), Diphyphyllum, Strombodes, and Omphyma. Haly sites
is the most characteristic fossil of the Silurian rocks of
the Rocky mountains, which are called the Halysites beds
in consequence.
GRAPTOLITES. True graptolites such as characterised the
Ordovician are far less
abundant in the Silurian
strata. There is, however,
a strong development of a
related type of creature in
which the skeleton is a
frond-like expansion com-
posed of numerous irregu-
lar branches; these are
called dendroid graptolites,
in allusion to their form.
They occur in great abun-
Dictyonema crassibasale from the Silurian at Hamil- danCC in the cherty layers
ton, Out. About one-half size. After Bassler. Q{ ^ Lockport formation
on the top of the mountain at Hamilton. Dictyonema is a
common and characteristic example.
STROMATOPOROIDS. These are very peculiar creatures, the
FIG. 105. SILURIAN DENDROID
GRAPTOLITE
FIG. IO6. STROMATOPOROIDS OF THE SILURIAN
i. Weathered specimen of a stromatoporoid showing the concentric laminae; 2. Vertical
section of a stromatoporoid (Clathrodictyon) showing'the horizontal laminae and vertical
pillars.
FIG. IOy. SILURIAN CRINOIDS AND CYSTIDS
i. Callocystis jewetti, a very perfect specimen from the Rochester shale at Grimsby, Ont.
2. Eucalyptocrinus ccelatus ; 3. Ichthyocrinus Icevis ; 4. Stephanocrinus angulatus
5. Caryocrinus ornatus. All figures seven-eighths natural size.
226
ELEMENTARY GEOLOGY
exact relationships of which are doubtful. The skeletons
consist of innumerable delicate laminae of carbonate of lime
placed only a fraction of a millimetre apart and connected by
FIG. I08. SILURIAN BRACHIOPODS
I. Conchidium decussatum, this large species is common in the Silurian of Manitoba;
2. Spirifer niagarensis ; 3. Dalmanella elegantulcf 4. Spirifer striatus; 5. Rhynchotreta
". cuneata americana ; 6. Hindella umbonata ; 7. Ccelospira planoco ivexa. All figures
^natural size. After Billings, Whiteaves, Hall, and photos.
little rods or pillars. In spite of their delicate structure the
skeletons reach large dimensions, sometimes feet in diameter;
in some places they build Up whole beds of limestone.
THE SILURIAN PERIOD
227
While stromatoporoids are not unknown in the Ordovician,
they .first reach a position of importance in Silurian time.
The strata of the lower and middle divisions in Ontario
contain many species, and whole layers of rock on the
Saskatchewan river are composed of their remains. Stro-
matopora, Actinostroma, and Clathrodictyon are common
genera.
FIG. IOQ. SILURIAN GASTROPODS
I. Platyceras niagarense ; 2. Diaphorostoma niagarense ; 3. Three species of Ccelocaulus ;
4. Liospira perlata ; 5. Pycnomphalus salaroides. Nos. i and 2 about four-fifths natural
size. Rochester shale, Grimsby; Nos. 3, 4 and 5 from casts from the Guelph dolomite;
No. 3 about one- third natural size; Nos. 4 and 5 about three-fourths natural size.
CYSTIDS. These creatures are less abundant than in the
Ordovician, but some highly-developed types still exist. The
Rochester shale has yielded some beautifully preserved forms
at '.Grimsby and other points along the Niagara cuesta.
Caryocrinus and Callocystis are typical.
CRINOIDS. Sea lilies are more abundant than in the Ordovi-
cian ; they occur in great numbers both in Europe and America,
but well-preserved specimens are not common in the Canadian
228
ELEMENTARY GEOLOGY
rocks. The best specimens have been obtained from tha
Rochester shale at Grimsby, and the overlying limestone
contains vast numbers of broken fragments. Stephanocrinus
and Eucalyptocrinus are the commonest genera.
BRACHIOPODS. Brachiopods occur in extraordinary numbers
FIG. HO. SILURIAN PELECYPODS AND CEPHALOPODS
I. Dawsonoceras annulatum, from a specimen from Ontario; 2. Phragmoceras lincolatum,
from a specimen from Keewatin; 3. Megalomus canadensis, large specimen with shell
from the Guelph formation of Ontario; 4. Megalomus canadensis, cast of the interior.
All figures about three-eighths natural size.
throughout the Silurian, occupying a position scarcely inferior
to that which they filled in the Ordovician. The hinged type
without arm supports is still dominant, but the more highly
developed brachiopod with complicated calcareous loops and
spirals for the support of the arms makes its appearance
THE SILURIAN PERIOD
229
in some abundance. Of the simpler type, the most character-
istic genera are Dalmanella and Rhy nchonella ; of the higher
type, A try pa, Ccelospira, and Spirifer.
GASTROPODS. These forms are increasing in numbers and
importance. Ordovician genera such as Hormoioma, Lopho-
spira, and Liospira still survive, and genera of less importance
in the Ordovician become very numerous, e.g. Platyceras and
Diaphorostoma. The Guelph formation contains a remark-
able assemblage of gastropods, many of them belonging to
new genera, e.g. Pycnomphalus.
PELECYPODS. The bivalves greatly resemble those of the
Ordovician seas: many of the genera are identical, but the
species are different. Megalomus canadensis is a very large
pelecypod characteristic of the Guelph formation, where it
occurs in remarkable abundance.
CEPHALOPODS. The nautiloid with straight shell is still
abundant and is represented by a number of genera, of
which Dawsonoceras will serve
as an example. Coiled and
curved forms are more com-
mon than in the Ordovician,
e.g. Phragmoceras.
TRILOBITES. Trilobites are
abundant, but they are some-
what past the supremacy they
enjoyed in Cambrian and
Ordovician time. The inter-
mediate type is still abundant,
but the highest type occurs
in increasing numbers. The
decline of the trilobites is
attributed to the incoming
of eurypterids and armoured
fish. Examples of the simpler
type are Acidaspis, Lichas,
and IllcBUUS, and Of
1-1 /^ i
higher type Calymene
OSTRACODS. These little
creatures are still abundant fossils.
FIG IIT SILURIAN TRILOBITES
the i. Dalmanites limulurus, Ontario; 2. Acidaspis
i perarmata, Lake Winnipegosis ; 3. Bumastus
and Lrriensis, a typical European species re-
sembling the American B. ioxus; 4. Lichas
bottom, a large type, sometimes seven inches
in length- Figures much reduced-
The Guelph formation of
230 ELEMENTARY GEOLOGY
Ontario shows several species, and they are particularly
abundant in the Silurian strata of northern Manitoba.
EURYPTERIDS. These very peculiar organisms are confined
to Palaeozoic time: they are probably related to the existing
king crab, but differ in many important
details. The animals were of very general
organisation and capable of swimming,
crawling on the bottom, or digging in
mud, but they were not specialised to
perform any of these functions in a very
perfect manner. Some of the species were
of great size, exceeding a metre in length.
FIG. 112. EURYPTERUS T^y first reach * position of importance
REMIPES toward the close of Silurian time. It is
About one -eighth natural significant that their appearance marks
size. From Clarke and . V -, • •, •, •
Ruedemann, " The Eury- the time of the decline of the tnlobites.
FISH. Fragmentary remains of fish have
been found in Ordovician rocks, but Silurian strata have
yielded the earliest fish fauna worthy of the name, as un-
doubted remains have been found in Europe, Pennsylvania,
New York, New Brunswick, and Newfoundland. The fish of
this time belong to two types: sharks and the remarkable
group known as Ostracoderms. The sharks are represented
chiefly by the hard granules of the dermal investment and
by spines. The ostracoderms are primitive organisms of fish-
like appearance and habit. Unlike all existing fish, however,
the head and trunk were covered with a thick, hard invest-
ment (armour plate), and the creatures were not possessed of
jaws. On the latter account some authors place the ostraco-
derms lower than the fishes and refer them to a separate
class, the Agnatha.
Silurian ostracoderms were more primitive than those of
the next period, and occur in much fewer number. An inter-
esting Canadian example is Cyathaspis acadica from the
Nerepis hills, King's county, New Brunswick.
Air-breathing invertebrates are represented for the first
time by primitive scorpions, e.g. Palceophonus, and by insects.
Before the close of the Silurian, as shown above, North
America had become more or less clothed with vegetation.
Psilophyton and other land plants crept over the rocks and
THE SILURIAN PERIOD
231
lifted their green stalks a few inches above them. The green
of land plants covered what had been the desolation of bare
rocks; and the finding of the scorpion and insects just
FIG. 113. PAL^OGEOGRAPHIC MAP OF NORTH AMERICA IN MIDDLE AND
UPPER DEVONIAN TIME
From Pirrson and Schuchert, " Textbook of Geology."
mentioned is suggestive of air-breathing animals feeding
upon the herbage. The earth already had its innocent
plant-feeding inhabitants and the predatory creatures that
devoured them.
CHAPTER VIII
THE DEVONIAN PERIOD
THE name Devonian is derived from the type locality in
Devonshire where rocks of this system were studied by the
great English pioneers of stratigraphic geology, Sedgwick
and Murchison. The system as developed in south-western
England is much contorted and broken, and its base has not
yet been revealed; in consequence, geologists in other parts
of the world have great difficulty in correlating their Devonian
strata with those of the type locality, and even in drawing
the line between the formations of Silurian and of Devonian
time. It is, perhaps, a matter of regret that the type region
for this great system had not been established elsewhere,
where fossils are better preserved and the limits of the system
better defined. Such regions are to be found in many parts
of the world, e.g. in the Rhine valley and in the State of New
York, where one of the most complete sequences of Devonian
rocks is known.
Before Devonian time diverse facies do not seem to have
added greatly to the difficulty of deciphering the history,
but in this period there is evidence of two very distinct
facies, and from this time on facies becomes a factor to be
carefully regarded.
Before the name Devonian was given to the strata of
south-western England, a great series of sediments in Scotland
had been called the Old Red. These strata contain no marine
organisms, but they abound in the remains of fishes and
plants; they are freshwater deposits, a freshwater facies,
whereas the English rocks belong to a marine facies. It is
now known that both these facies are of Devonian age;
they are recognised in various parts of the world, and are
found in Canada.
PHYSICAL EVENTS OF THE DEVONIAN IN
NORTH AMERICA
We have seen that emergent conditions prevailed towards
the close of Silurian time, with the result that practically
232
THE DEVONIAN PERIOD 233
the whole of the present area of North America became land.
Devonian time was ushered in by an invasion of the sea into
narrow troughs in the Acadian region of Canada, the Appala-
chian region of the United States, and the Rocky Mountain
geosyncline of the west; also, a flood advanced northward
from the Gulf of Mexico. This epoch of narrow seas con-
stitutes the Lower Devonian.
A greater subsidence of the continent followed, permitting
the union of the waters from the Gulf with those from the
Atlantic, and an advance northward of the united flood over
a considerable portion of the continental interior. In the
Cordilleran area, also, there was a considerable advance of
the oceanic waters. This time of maximum depression and
flooding is the Middle Devonian.
The later or Upper Devonian epoch saw a gradual elevation
of the continent, with a consequent draining away of these
seas over the whole of its area.
In the Acadian region, terrestrial movements of a marked
kind characterised the Devonian as the land mass was gradu-
ally raised and the rocks much folded and twisted. These
movements were accompanied by upwellings of molten
matter from the interior of the earth and the consequent
formation of great granite masses, as at St. George, New
Brunswick, and in the Little Megantic mountains and other
places in the province of Quebec. Flows of volcanic rock, in
all probability of Devonian age, occur in many parts of
Nova Scotia and New Brunswick. The remarkable series of
isolated mountains, known as the Monteregian hills, which
arise abruptly from the Palaeozoic plain of western Quebec
and stretch from Montreal mountain to Brome mountain,
are regarded as the pipes of Devonian volcanoes of which all
other evidence has long since disappeared.
THE DEVONIAN SYSTEM IN CANADA
In North America Williams recognises four great provinces
of Devonian rocks, each of which carries a fauna of distinctive
character which reveals more or less clearly the oceanic basin
or basins from which it has been derived. These provinces are :
234 ELEMENTARY GEOLOGY
Eastern Border Province — Maritime provinces and Maine.
Eastern Continental Province — Southern and east central
states, the province of Ontario, and the region south of
Hudson bay.
Interior Continental Province — Iowa, Minnesota, Illinois,
Manitoba, and the Mackenzie River district.
Western Continental Province — Great Basin region, Nevada,
etc.
Without regard to faunal provinces, the Devonian rocks of
Canada fall naturally into geographical areas as below:
FIG. 114. SKETCH MAP OF EASTERN CANADA SHOWING THE CHIEF
AREAS OF DEVONIAN ROCKS
Undoubted Devonian, black; mixed Devonian and Carboniferous, dotted. Other small areas
occur in Nova Scotia and New Brunswick, particularly in the northern part of the dotted
region in Figure 102.
i. ACADIAN AREA. Narrow and isolated belts of Devonian
rocks disposed in a north-east and south-west direction occur
at a number of places in Nova Scotia, New Brunswick, and
Gaspe. In Nova Scotia, these rocks form an interrupted belt
reaching from Minas basin to the Strait of Canso. In Cape
Breton, rocks of this system occur near Hawkesbury in
Southern Inverness, on Madame island, and at several points
in Richmond county.
In New Brunswick, the Devonian strata are confined to
small areas in the southern part of the province. A much
larger belt extends through the peninsula of Gaspe from its
eastern extremity to the Matapedia river. This area is
THE DEVONIAN PERIOD
235
important, as it presents the best section of the Lower Devonian
rocks to be found in Canada. Outliers of this area along
Chaleur bay and on the Restigouche river are of Upper
Devonian age and continental origin; they are comparable
with the Old Red of Scotland, and contain the remains of fish
and terrestrial plants.
The Devonian rocks of the Acadian region are sandstones,
limestones, shales, and conglomerates; in Nova Scotia and
New Brunswick they are much contorted and broken by
subsequent earth movements. The strata of the Gaspe area,
however, are less disturbed and contain some heavy beds of
sandstone suitable for structural purposes.
2. ONTARIO AREA. Devonian rocks form practically the
whole of the western peninsula of Ontario west of a line from
Fort Erie on Lake Erie to Port Elgin on Lake Huron. The
rocks include sandstone, limestone, and shale. The lowest
Devonian rocks are not present, as the sea had not advanced
into this region until late in Lower Devonian time. The
deposits belong, for the most part, to the period of maximum
flood in Middle Devonian time. The following table, modified
from Stauffer, indicates the formations of the Devonian of
Western Ontario.
THE SEQUENCE OF DEVONIAN ROCKS IN ONTARIO
SYSTEM
SERIES
FORMATION
MEMBER
Devonian
Upper
Devonian
Portage and Chemung
Port Lampton beds
Genesee
Huron shale
Middle
Devonian
Hamilton
Ipperwash limestone
Petrolia shale
Widder beds
Olentangy shale
Delaware
Delaware limestone
Onondaga
Onondaga limestone
Springvale sandstone
Lower
Devonian
Oriskany
Oriskany sandstone
236 ELEMENTARY GEOLOGY
In a general way it may be said that these ^formations,
from the lowest to the highest, are encountered as one passes
westward across the area.
The Oriskany sandstone rests unconformably on the
Silurian rocks; it is of very limited extent, and is quarried
near Cayuga for use as a lining in acid hearth furnaces on
account of its highly siliceous character.
The centre of the region is occupied by the Middle Devonian
limestones; they are quarried for cement-making, for con-
crete, and for building. The petroleum of Oil Springs and
Petrolia is derived from strata of this age.
The Huron shale of the Upper Devonian series is remark-
able on account of containing large spherical concretions of
brown calcite, which sometimes reach a diameter of several
feet. Kettle point on Lake Huron received its name from the
fact that the partially submerged concretions along the shore
resemble inverted sugar kettles. The shales are bituminous,
and may become a source of oil.
3. JAMES BAY AREA. A large area of Devonian rocks
occurs in the region immediately south-west of James bay.
The fossils resemble those of the Ontario area, and suggest
that the rocks were formed in the same sea. In support of
the conjecture that the Devonian seas were continuous across
the highlands of Ontario, may be mentioned the occurrence
of scattered Devonian fossils and even the outcrops of isolated
layers of Devonian limestone at different places in the Pre-
cambrian region of Northern Ontario, particularly on the
Kenogami river, as recorded by Professor Parsons.
Large beds of gypsum are exposed on the Moose river and
at other points in the region, and will prove of great value if
the country is ever settled.
4. MANITOBA-MACKENZIE RIVER AREA. Devonian rocks
pass in a north-westerly direction diagonally across the pro-
vince of Manitoba, with a width of about 50 miles: Lakes
Manitoba and Winnipegosis lie very largely within this belt.
After some interruption, owing to covering by later rocks,
the system again appears to the north-west, and with gradu-
ally increasing width extends nearly to the mouth of the
Mackenzie river. An immense area to the south of Great
Bear lake and to the west and south of Great Slave lake is
THE DEVONIAN PERIOD 237
occupied by rocks of this system. As the Devonian strata
rest directly on the old Pre-cambrian axis in the northern
part of this area, it is evident that the Devonian flood reached
wide dimensions in this region. The fossils found in these
rocks indicate that the fauna belonged to a sea which did not
communicate with that in which the Ontario and James Bay
rocks were deposited.
The Devonian rocks of Manitoba are subdivided as follows:
Manitoban.
Winnipegosan.
Elm Point.
The lower or Elm Point formation consists of thin-bedded
limestones overlying red shales: the rocks are typically
exposed at Elm Point and Steep Rock on Lake Manitoba.
The limestones are extensively quarried for cement-making
and lime-burning.
The Winnipegosan formation is a highly dolomitic lime-
stone which may be seen to best advantage on the east shore
of Dawson bay, Lake Winnipegosis, where it forms steep
and picturesque cliffs.
The Manitoban formation is composed largely of almost
pure limestone, which is much more heavily bedded than the
strata of the Elm Point formation. Cliffs on the west side of
Dawson bay, and on Snake island in Lake Winnipegosis,
afford numerous fossils characteristic of the formation.
The following classification of the Devonian strata of the
Mackenzie River district has recently been published:
FORMATION
CORRELATION
Upper Devonian
Hay River limestone
Hay River shales
Simpson shales
Chemung
Chemung
Portage
Middle Devonian
Slave Point limestone
Presqu'ile dolomite
Pine Point limestone
Manitoban
Winnipegosan
Elm Point
5. ROCKY MOUNTAIN AREA. Devonian limestones accumu-
lated to a great thickness in the Rocky Mountain geosyncline,
238 ELEMENTARY GEOLOGY
and now form a conspicuous element in the easterly ranges
of the mountains. Three formations are recognised as follows :
Lower Banff limestone.
Intermediate limestone.
Sawback limestone.
The Lower Banff limestone is the most conspicuous forma-
tion ; it is a hard and rather dark limestone with a thickness
of 2000 feet in the Rockies of southern Alberta. This forma-
tion forms the conspicuous lower knee of the mountain shown
in Figure 129. Fossils are few and poorly preserved in the
Devonian rocks of the mountains, and our knowledge of the
northward extent of the system is very limited. The Cordil-
leran sea is thought to have been continuous with that in
which the Manitoba-Mackenzie River rocks were formed.
LIFE OF THE DEVONIAN
Fossils are extremely abundant in Devonian rocks in all
parts of the world; even in Arctic and Antarctic regions,
species are found which indicate temperate to sub-tropical
conditions. It is a fair conclusion that the climate of Devonian
time was genial over the whole earth, a condition very favour-
able to the development of great numbers of animals, but
perhaps not so favourable to the development of new orders.
Devonian life differs from that of the Silurian, not in the
introduction of many new groups of organisms, but in the
decline of paramount groups of the Silurian and the great
development of types which played but a small part in that
period. Cystids and graptolites, so characteristic of Silurian
and Ordovician time, are practically unknown. Trilobites
have seriously declined and brachiopods are somewhat less
abundant. On the other hand, terrestrial plants reach a
position of great importance; gastropods and pelecypods
increase; and there is a development of corals and fish so
remarkable that the period has been called The Age of
Corals and Fish.
While the difference between the life of the two periods
consists largely in the relative development of the classes of
THE DEVONIAN PERIOD
239
organisms, there is, nevertheless, a substantial difference whe*i
the two faunas are compared in any detail, as the following
brief summary will show:
DEVONIAN PLANTS
The lowly Psilophyton of the Silurian was the forerunner of
a terrestrial flora which consisted very
largely of vascular cryptogams or spore-
bearing plants, but some primitive gymnos-
perms are known as well. As this flora
reached a greater development in the period
following the Devonian, its consideration
will be deferred until the Carboniferous
system is taken up.
In Canada, as most of the rocks are of
marine origin, the remains of plants are not
common. In the Acadian region, however,
many species have been found, particularly
in the continental Devonian of Gaspe.
DEVONIAN INVERTEBRATES
FIG. 115. SILURIAN
AND DEVONIAN
PLANT
Psilophyton princeps, one
of the earliest land
plants from the De-
vonian sandstone of
Gaspe. Reduced.
After Dawson.
SPONGES. While these organisms are not
particularly abundant throughout the sys-
tem, some of the fine sandy shales of the Upper Devonian
in the State of New York have yielded a remarkable number
of delicate siliceous sponges, some of which attained a length
of a foot or more (Dictyospongidcs) .
CORALS. Corals reached a wonderful development in the
warm Devonian seas and contributed much to the formation
of limestone, more particularly where they were segregated
into reefs. As corals live at definite depths in the sea, dislike
muddy water, and tend to a colonial manner of life, it is not
to be expected that all Devonian rocks will show their
remains in equal profusion. Many of the shaly members
of the system and some of the limestones are entirely
without corals.
The genus Favosites, already referred to in the description
of Silurian life, is represented by a great number of species,
and the related genus MicheMnea (bee's-nest coral) is likewise
240
ELEMENTARY GEOLOGY
abundant. Of the single type of coral, Cyathophyllum and
Heliophyllum are common; while Diphyphyllum, Crepido-
phyllum, and Phillips-
aster are examples of
the compound type.
The Onondaga for-
mation in the vicinity
of Port Colborne, On-
tario, contains vast
numbers of corals
which have been con-
verted into silica, and
consequently weather
out on the surface as
the limestone decays.
FIG. 1 1 6. SLAB OF ONONDAGA LIMESTONE The banks of the Aux
of?o^TT<f RI° SH°WING THE PROFUSION Sables river in Lamb-
OF FOSSILS 4
ton county, Ontario,
yield fossil corals in an exquisite state of preservation.
STROM ATOPOROIDS. These peculiar reef-building organisms
form whole layers of limestone of many feet in thickness.
Petoskey, Michigan, and Kelly island in Lake Erie are well-
known localities for the collecting of stromatoporoids ; they
are also abundant in the rocks of the James Bay area. These
organisms will not be referred to again as they do not survive
the Devonian, at least in America.
ECHINODERMS. Cystids have become so rare that they may
be said to be practically extinct. Crinoids are steadily in-
creasing, but they are so similar to the Silurian type that it
is difficult to express the difference in general terms. The
commonest Canadian genera are Megistocrinus, Dolatocrinus,
and Arthracantha.
Blastoids are echinoderms which seem to replace the
cystids; although known in lower formations, they first
assume a position of importance in the Devonian. Like
cystids and crinoids, they are cup-shaped, plated organisms
anchored to the sea floor by a jointed stem. The plates of the
cup are very regular in arrangement, more so than in crinoids
or cystids, from which they also differ by having the food-
gathering plumes arranged along the edges of five V-shaped
THE DEVONIAN PERIOD
241
notches in the upper margin of the cup. Codaster is a very
primitive blastoid, and is common in the Hamilton strata of
the Aux Sables river, Ontario; Granatocrinus and Pentre-
mitidea are more advanced types from the same locality.
BRYOZOA. These organisms are still very abundant, but
the type with long tubular cells is giving place to a short-
FIG. Iiy. DEVONIAN CORALS
i. Michelinea convexa ; 2. Phillipsaster billingsi ; 3. Favosites billingsi ; 4. Streptelasma
prolificum; 5. Heliophyllum halli; 6. Syringopora hisingeri. All figures about five-
sixteenths natural size from specimens from Ontario.
celled kind in which the little individuals inhabit pits which
are arranged along the ribs of an open, lace-like frond. The
gerius Fenestella, which first appeared in the Silurian, is
represented by a great many species.
BRACHIOPODS. Brachiopods continue to be the most
abundant shell-fish, only slightly less in relative importance
than in the Ordovician and Silurian.
Q
242
ELEMENTARY GEOLOGY
FIG. 1 1 8. DEVONIAN CRINOIDS AND
BLASTOIDS
i and 2. Dolatocrinus canadensis; 3. Ancyrocrinus
bulbosus (roots); 4. Arthracantha punctobranch-
iata; 5. Cadaster canadensis; 6 and 7. Pentremi-
tideafilosa; 8. Granatocrinus leda. Figures i to 6
half size, Figures 7 and 8 natural size.
Many of the Silurian genera have disappeared, while others,
e.g. Spirifer and A try pa, attain their maximum develop-
ment. Brachiopods with-
out arm-supports are re-
latively less abundant,
and are represented by
such genera as Stropheo-
donta and Chonetes. The
more highly - developed
forms with spiral or
looped arm-supports rule
in this period — e.g. Spiri-
fer, Atrypa, Athyris, and
Cvrtina with spires, and
' . A
StnngOCephdlUS, CentrO-
•,, j T> r_ , i
nelld, and 1 ereoratUta
with loODS
PELECYPODS AND GASTROPODS. These molluscs show a
steady advance on the position they occupied in Silurian time ;
the general type, however, is practically the same. Of gas-
tropods, Diaphorostoma, Euomphalus, and Platycems are
the most abundant; while the pelecypods are represented
by Conocardium, Aviculopecten, Grammy sia, and numerous
other genera.
CEPHALOPODS. The nautiloid shells, so characteristic of
Ordovician and Silurian time, still occur in abundance, and
are represented by the old straight-shelled type, Orthoceras]
the sack-shaped type with restricted apertures, Gomphoceras
and Phragmoceras; the curved type, Cyrtoceras; and the
coiled type, Gigantoceras and Centroceras.
In addition to the cephalopods of this kind, there occurs
for the first time a new type which is destined to replace the
nautiloids and to become the dominant creature of a later
era. The nautiloid shell has been described on page 213 ; the
new cephalopod differs in that the suture, or line of union
between the partitions and the shell proper, is not simple as
in the nautiloids, but angulated and folded. The primitive
forms of the new type, as seen in the Devonian, show a
comparatively simple angulation of the sutures and are
known as clymenoids.
FIG. Iig. DEVONIAN BRACHIOPODS
I. Spirifer pennaius arkonensis; 2. Spirifer pennatus thedfordensis; 3. Cyrtina hamil-
tonensis; 4. Stropheodonta incequistriata; 5. Chonetes coronatus; 6. Atrypa reticularis-
7. Rhipidomella vanuxemi; 8. Athyris spiriferoides. All figures seven-eighths natural
size, from specimens from Ontario.
FIG. 120. DEVONIAN PELECYPODS AND GASTROPODS
I. Conocardium trigonale; 2. Aviculopecten parilis; 3. Plcuronotus decewi; 4. Platvceras
qmnquesmuatum; 5. Diaphorostoma lineatum. After Billings, Whiteaves, and Hall.
244
ELEMENTARY GEOLOGY
TRILOBITES. The trilobites show a marked decline in the
Devonian; nevertheless, many new species appear which
belong for the most part to genera already introduced in
FIG. 121. DEVONIAN CEPHAI.OPODS
i. Gigantoceras inelegans; 2. Tornoceras uniangulare-, 3. Poterioceras eximium; 4. Cen-
troceras ohioense. All figures much reduced. After Hall.
the Silurian. Common examples are Phacops, Proetits, and
Dalmanites.
EURYPTERIDS are still abundant; the higher crustaceans
are increasing, and terrestrial
air-breathing invertebrates are
much more prominent than in
the earlier periods.
INSECTS. Insects like our
mayflies are known from near
FIG. 122. DEVONIAN TRILOBITES St. John, N.B., Pldtyphemera
i. crypkaus boothi; 2. Prottus rowi; 3. Pha- antiQua, with a five-inch spread
copsrana. Half size. After Hall. r • T^ c JJ ±Tk' 1
of wing. Dr. Scudder thinks
that one 'insect, Xenoneum antiquorum, was possessed of
a chirping organ.
THE DEVONIAN PERIOD 245
DEVONIAN VERTEBRATES
FISH. Fish made their first appearance in the Ordovician
period, and reached but a feeble development in the Silurian ;
in the Devonian, however, they attained a position of great
importance. Remains of fishes are extremely abundant in
the Old Red Sandstone of Scotland, and many examples are
known from the deposits of similar facies in the Acadian
region of Canada. The truly marine Devonian also has fur-
nished fossil fishes in both Ontario and Manitoba.
The different types of fish represented in Devonian time
are briefly described below:
Ostracoderms. Jawless, fish-like organisms, without paired
FIG. 123. TYPICAL DEVONIAN OSTRACODERM
Bothriolepis canadensis. Much reduced. After Patten.
fins, and with the head and anterior portion of the trunk
covered with plates. Cephalaspis has a large triangular head
shield, and the body is covered with quadrangular scales.
Five species are known from New Brunswick and Quebec.
Bothriolepis canadensis is a more highly developed ostra-
coderm from Scaumenac bay, Quebec; in this fossil there
are separate head and body shields each composed of a number
of plates, also a pair of pectoral fins or "rowing arms" like-
wise covered with plates and articulated to the angles of the
head shield. This remarkable organism is closely related to
the better known Pterichthys, of which many species are
known in different parts of the world.
Sharks. Using this term in the widest sense, the Devonian
period presents a great number of different types, some of
which are known only by teeth or spines, while others are
246
ELEMENTARY GEOLOGY
preserved in a manner to show the whole outline of the animal.
Cladoselache is a very primitive form from the Devonian
rocks of Ohio, and Pleuracanthus is likewise a simple form
which is not known in Canada, although teeth of related
genera are found in New Brunswick. Small spiny fish known
as acanthodians are represented by eight species in the
Devonian rocks of Quebec and New Brunswick. The presence
of large, shark-like fish is attested by the presence of spines
known as ichthyodorulites, of which Machcer acanthus will serve
as a Canadian example.
Lung-fishes. These peculiar fish, in which the air bladder
is modified into a breathing organ (lung), are of rare occur-
rence at the present time, but in the Devonian period they
FIG. 124. JAWS OF THE "TERRIBLE FISH*'
Dinichthys hertzeri, from the Devonian shales of Ohio. Much reduced. After Newberry.
seem to have played a very important role. Scaumenacia
curia is the best known Canadian example, from the famous
region of Scaumenac bay, Quebec. A peculiar group of fish,
probably related to the lung-fishes, is the Arthrodira, in
which the head and trunk are protected by thick plates, as in
the ostracoderms. Some of these fish reached extraordinary
dimensions, e.g. Dinichthys measured more than a metre
across the head. Coccosteus from Quebec, Macropetalichthys
from Ontario, and Dinichthys from Manitoba are the best
known Canadian examples.
Ganoids. Although the line of separation between the
ganoids and the true bony fish, or teleosts, is very indistinctly
marked, a ganoid may be distinguished by the possession of
a cartilaginous skeleton and thick rhomboidal scales, instead
of the bony skeleton and thin flexible scales of the teleost.
The most primitive ganoids, the Crossopterygii, were parti-
THE DEVONIAN PERIOD
247
cularly abundant in and characteristic of Devonian time.
These fish possessed "fringed fins," i.e. the fin had a central
FIG. 125. DEVONIAN FISH
i. Scaumenacia curta, Canadian lung-fish; 2. Cheirolepis canadensis, Canadian heterocerca
ganoid fish; 3. Holoptychius quebecensis, Canadian fringe-finned ganoid; 4. Eusthen-
opteron foordi, Canadian fringe-finned ganoid. Figures i and 2 about one-fourth natural
size, Figures 3 and 4 about three-eighths natural size. After Traquair and Whiteaves.
axis from which the fin-rays sprang out on two sides, and
the joints of the backbone continued to the tip of the tail
(diphycercal) . Holoptychius, a stout fish of two feet or more
248
ELEMENTARY GEOLOGY
in length, is the best known example, and is represented by
Holoptychius quebecensis from Scaumenac bay.
The heterocercal ganoids, in which the paired fins have no
scaly axis, and in which the termination of the vertebral
column turns up into the dorsal lobe
of the caudal fin, are of less frequent
occurrence than the crossopterygian
fish; nevertheless, they begin their
existence in Devonian time and reach
a remarkable development later.
Cheirolepis canadensis is the only
Canadian example.
The Devonian fish fauna is remark-
able on account of its rapid develop-
ment, the variety of forms represented,
Head shieT/on7e^oured fish, the bizaiTe shaP6 °f many °f its mem-
cephaiaspis campbeiitonensis. bers and the size and ferocity of others,
About one-third natural size. . .... ..,, , .
its coincidence with the decline of the
trilobites, and the evidence it affords of the futility of armour,
as none of the plated fish survive the Devonian period.
AMPHIBIA. The higher air-breathing vertebrates seem to
FIG. 126. DEVONIAN
OSTRACODERM
FIG. 127. KETTLE POINT, LAKE HURON
Port Huron shales with concretions of carbonate of lime.
have made a beginning in the Devonian, but the evidence
is not very extensive. A single footprint from the Upper
THE DEVONIAN PERIOD 249
Devonian of western Pennsylvania is thought to attest the
presence of a forerunner of the amphibians of the next
great period.
On the land great advances took place during the Devonian ;
the creeping club mosses had aspired to become trees, and
in Eastern Canada there seem to have been the stiff uncouth
beginnings of forests. Air-breathing animals, too, had pro-
gressed so far that numerous insects flitted among the trees:
these creatures probably possessed chirping organs; the
country was no longer voiceless.
CHAPTER IX
THE CARBONIFEROUS PERIOD
THE closing stages of the Palaeozoic era were marked by such
varying conditions in different parts of the world that the
strata are with difficulty arranged in correlated groups or
even in comparable systems for the different continents.
European geologists recognise two great systems, the Carboni-
ferous and the Permian. In India, South Africa, and Aus-
tralia, while true Carboniferous rocks are recognised, the
upper or Permian system is so ill denned that the term
Permo-Carboniferous is adopted for the later rocks. In
North America the lower strata are so well developed in the
Mississippi valley, and so sharply marked off from the over-
lying rocks, that they are thought to represent a great system
in themselves: this system is known as the Mississippian,
and is comparable with the Lower Carboniferous of European
geologists. The rocks above the Mississippian likewise form
a very distinct unit and are embraced in a great system, the
Pennsylvanian, by American geologists. The highest strata
of all, which one would expect to correlate with the Permian
of Europe, are so feebly developed and fade so imperceptibly
into the underlying Pennsylvanian rocks that they may be
included in that system.
CORRELATION TABLE OF THE CARBONIFEROUS AND
PERMIAN OF EUROPE AND NORTH AMERICA
EUF
OPE
NORTH AMERICA
System
Series
System
Permian
Permian
Pennsylvanian
Upper Carboniferous
Lower Carboniferous
Mississippian
• -
250
THE CARBONIFEROUS PERIOD 251
The great terrestrial movements which have determined
the definition of systems in North America have naturally
affected Canada as well as the United States; therefore, it
would seem to be advisable to adopt the nomenclature of
the geologists of the United States. On the other hand, it
does not seem advisable to leave out of the literature the old
term Carboniferous in an elementary work intended to
give a general survey of geological history.
The term Carboniferous owes its origin to the fact that
the strata contain a great amount of carbon in the form of
beds of coal. The practice of naming systems or formations
according to the kind of rock was quite common in the early
days of the science, but it has been abandoned in favour of
the use of geographic terms. European geologists recognise
two subdivisions of the Carboniferous system, a lower series
with predominating limestones representing sedimentation
in a deep sea, and an upper series which carries the coal and
is consequently known as the "Coal Measures."
PHYSICAL EVENTS OF THE CARBONIFEROUS
IN NORTH AMERICA
The advancing seas of early Carboniferous time invaded a
continent which had largely emerged by the close of the
Devonian period. These waters extended northward from
the Gulf of Mexico, and gradually spread over a great area
in the region of the Mississippi river and northward into
Michigan, Ohio, and Pennsylvania. At the same time the
Rocky Mountain geosyncline was flooded, probably into
Arctic regions, and fossils entombed which suggest a connec-
tion between the' Cordilleran and mid-continental basins.
A third limited area of invasion was in the Acadian region of
Canada, where the seas advanced over upturned Devonian
rocks, on which their deposits now rest with pronounced
unconformity. The fossils from this area are very different
from those of the mid-continental and Cordilleran regions,
and indicate that there was no communication across the
Alleghanian highlands. A retreat of the sea, abrupt in the
Cordilleran region but more gradual in the mid-continental
252 ELEMENTARY GEOLOGY
region, brought the Mississippian or Lower Carboniferous
epoch to a close.
Upper Carboniferous (Pennsylvanian) time was marked in
eastern North America by slight crustal movements and
shallow invasions of the seas into more or less land-locked
basins, wherein were deposited the great accumulations of
vegetable matter which have subsequently become coal.
Greater terrestrial movements affected the Pacific border
of the continent in the Upper Carboniferous epoch. The seas
advanced for the first time on the western flank of the old
land, which throughout long ages had existed to the west-
ward of the Rocky Mountain geosyncline. The deposits of
this sea are distinctly marine, and they never contain coal;
on the other hand, the sedimentary rocks are frequently
mingled with volcanics, indicating a state of great unrest in
the terrestrial crust of this area.
COAL
Accumulations of vegetable matter, buried in the rocks
and subsequently subjected to the pressure exerted by the
overlying rocks or by crustal movements, are altered into
coal. It is apparent that the character of the coal will vary
with the degree to which these forces have acted: if the pres-
sure is slight and the duration of action not too long, the
resulting coal will be woody and the gaseous constituents of
the original matter will be expelled to a minimum degree.
On the other hand, heavy forces acting for a long time will
so alter the original matter that it will be reduced to the
condition of carbon, and the gaseous constituents will be
largely expelled. Between these extremes lie all possible
stages in the gradual transformation of woody matter
into coal.
The more important constituents of coal are carbon (un-
combined or fixed carbon), volatile matter, ash, and water.
The relative percentages of these ingredients determine, to a
very large extent, the commercial classification of coals. The
varieties more commonly recognised are as follows:
LIGNITE. The least altered type, with low fixed carbon and
THE CARBONIFEROUS PERIOD 253
water up to 20 per cent. They are soft, are liable to disintegra-
tion, and are of relatively low heating power.
SUB-BITUMINOUS. Coals with low percentage of fixed carbon
and 6 per cent, or more water. They are intermediate between
lignites and bituminous coals.
BITUMINOUS. Coals with 12 to 35 per cent, of volatile matter
are sometimes called humic or soft coals. They contain much
volatile matter, and consequently burn readily with pro-
nounced flames. When coals of this class burn without a
tendency to fuse together they are called non-coking; when
they exhibit this property they are coking coals, and are
valuable for the making of coke. Cannel coal is a highly
gaseous type of fine grain and dull lustre; it is used for gas-
making and for domestic heating in grates.
SEMI-ANTHRACITE. Coals with 7 to 12 per cent, of volatile
matter. They are non-coking and burn freely and quickly
with the production of yellow flames and intense heat; in
consequence, they are of particular value for the rapid raising
of steam and for use in forges.
ANTHRACITE. Hard coal with 3 to 5 per cent, of volatile
matter. Anthracite burns with an intense heat and scarcely
any flame: it is comparatively clean to handle and produces
a minimum of sooty gases, and in consequence is highly
desirable for domestic use.
Accumulations of vegetable matter of sufficient extent
eventually to make beds of coal have been formed during
many of the geological periods from the Devonian onward.
In Upper Carboniferous time, however, these accumulations
were so much greater than in any other epoch that the bulk
of the world's supply of coal is obtained from strata of this
age. The strata containing the beds of coal were called the
"Coal Measures" by the early geologists, and the term is still
used, but not commonly, as a formational name. The Coal
Measures consist of layers of sandstone, shale, and coal with
a minimum of limestone. As marine fossils are seldom, if ever,
found in the measures, we must conclude that the vegetable
matter accumulated in freshwater marshes or in marshes
originally salt, but which became brackish and eventually
fresh by the cutting off of communication with the open sea.
The underclay beneath the coal beds frequently shows the
254 ELEMENTARY GEOLOGY
roots of trees, and erect trunks have been found in many
places, e.g. at the South Joggins, Nova Scotia. It is con-
cluded, therefore, that the coal-forming plants grew in situ,
although there is evidence that in some cases the vege-
table matter had been drifted into the position in which
the coal is found.
The occurrence in the same section of numerous beds of
coal separated by layers of sandstone and shale bears witness
to the oscillatory character of the waters; and the presence
of beds of coal, sometimes many feet in thickness, can be
accounted for only on the assumption of a gradually
sinking bottom.
THE CARBONIFEROUS SYSTEM IN CANADA
Carboniferous rocks occur only in the extreme east and the
extreme west of the Dominion; three general areas may be
recognised as below:
i. ACADIAN AREA. Carboniferous rocks occupy a large
triangular district of about 10,000 square miles in the province
of New Brunswick, and form a somewhat broken belt across
the province of Nova Scotia from the Bay of Fundy to Sydney
harbour in Cape Breton. Across Cabot strait beds of this
age reappear on the western side of Newfoundland.
The Carboniferous rocks of this area are classified as follows :
SUBDIVISIONS OF THE CARBONIFEROUS ROCKS IN
EASTERN CANADA
SYSTEM
SERIES
FORMATION
Coal Measures
Upper Carboniferous
Millstone Grit
Carboniferous
Lower Carboniferous
Windsor (local)
Other local formations
The Lower Carboniferous rocks are coarse elastics indicating
rapid deposition, limestone with the fossils characteristic of
the time, and beds of gypsum which are extensively mined
in both provinces.
THE CARBONIFEROUS PERIOD 255
The Albert shale, a formation of Lower Carboniferous or,
possibly, Devonian age, in New Brunswick is so strongly
impregnated with
hydrocarbons that
oil and ammon-
ium sulphate may
be obtained in
commercial quan-
tities by distilla-
tion. Layers of
sandstone associ-
ated with these
shales yield both
petroleum and
natural gas. The
production of pe-
troleum is small,
but natural gas is
supplied to Monc-
ton, Hillsboro, and
other places. The
output in 1913
was 800,000,000
cubic feet, but in 1915 it had fallen to 430,000,000 cubic feet.
The natural alteration of seepages of petroleum from the Albert
shale has resulted in the formation of veins of a black shining
mineral called albert it e. This substance was mined for more
than thirty years and employed as a high-grade gas coal : the
supply is apparently exhausted.
The Millstone grit is of wide extent, and constitutes nearly
all of the large district in New Brunswick. The rocks are
chiefly sandstones, suitable for building and for the making
of grindstones and pulpstones. The strata are conformable
with the overlying Coal Measures, and contain thin seams of
coal which are worked to a limited extent in New Brunswick.
The Coal Measures consist of alternating beds of shale
and coal mingled with sandstones similar to those of the
Millstone grit.
Coal-mining in Nova Scotia is one of the most important
industries in Canada: more than 65,000,000 metric tons have
FIG. 128. SKETCH MAP OF EASTERN CANADA SHOW-
ING THE EXTENT OF CARBONIFEROUS ROCKS
Lower Carboniferous, dotted; Upper Carboniferous, black;
Permo-Carboniferous, vertically lined.
256
ELEMENTARY GEOLOGY
been mined, and it is estimated that the coal fields contain
a reserve of 7,500,000,000 tons capable of being worked. The
coal is of the bituminous type, with the variety cannel coal
FIG. I2Q. ROCKY MOUNTAINS NEAR BANFF, ALBERTA
The lower knee to the left is the Lower Banff limestone; the darker, more sloping section
above is the Lower Banff shale; the upper knee is the Upper Banff limestone covered
t by the Rocky Mountain quartzite at the top... Mines Branci, Dept. of Mines, Canada.
in limited amount,
productive regions:
The following table indicates the chief
THE COAL FIELDS OF NOVA SCOTIA
COAL FIELD
SUBDIVISION
Cumberland
Joggins
Springhill
Pictou
Westville
Stellarton
Vale
Inverness
Port Hood
Mabou
Broad Cove
Sydney]
Cajte Dauphin
Glace Bay
Victoria- Lingan
Sydney Mines
THE CARBONIFEROUS PERIOD 257
2. ROCKY MOUNTAIN AREA. The great Rocky Mountain
geosyncline continued to be an area of deposition during the
Carboniferous; in consequence, strata of this age are found
to a great thickness in the mountains of British Columbia
and Alberta. The rocks extend far to the north, but their
exact limits have not yet been ascertained. The great ranges
of the Eastern Rockies overlooking the plains are capped by
Carboniferous rocks of which three formations are clearly
shown, at least in the southern part of the ranges. Near
the line of the Canadian Pacific Railway these formations
are as follows:
CARBONIFEROUS FORMATIONS OF THE SOUTHERN
ROCKIES
SERIES
FORMATION
THICKNESS
ROCKS
Upper
Carboniferous
Rocky Mountain
Quartzite
800 feet
Hard, white
quartzite
Upper Banff
Limestone
2300 feet
Hard, compact
limestone, cherty
in places
Lower
Carboniferous
Lower Banff
Shale
1 200 feet
Hard, dark-
coloured shale
The difference in hardness of the limestone, shale, and
quartzite gives the formations a clear definition on the cliff-
face of the mountains. The superior hardness of the Rocky
Mountain quartzite causes it to form the summits of the
ranges, as all the later and softer rocks which originally over-
laid it have been removed by erosion.
The Rocky Mountain quartzite contains certain beds
carrying a small amount of phosphoric acid. These have
been suggested as a source of phosphorus, but they have not
yet been proved to be of economic value.
3. WESTERN BRITISH COLUMBIA AND PACIFIC COAST AREA.
In 'Upper Carboniferous time the lands which had existed
for long ages in western British Columbia sank beneath
the waters of the Pacific ocean, and strata of this age
were deposited over very large areas to a thickness, in
places, of at least 9500 feet. The formation has been called
R
258
ELEMENTARY GEOLOGY
the Cache Creek group, and consists of a lower series of
shaly rocks and an upper series of limestone. Volcanic activity
was pronounced, and igneous rocks, both effusive and frag-
mental, are mingled with the sedimentaries. The actual
areas covered by these rocks can scarcely be indicated, as
they have been much eroded and hidden by later rocks both
igneous and sedimentary.
LIFE OF THE CARBONIFEROUS
CARBONIFEROUS PLANTS
The Carboniferous flora consists essentially of vascular
cryptogams, with an admixture of primitive seed-bearing
plants. The cryptogams were
undoubtedly the chief coal-
forming plants, as they lived
in the low marshes so charac-
teristic of the period. The
seed-bearing plants likewise
contributed to the making of
coal, as their remains are found
together with those of the
cryptogams.
The vascular cryptogams, or
Pteridophyta, were represented
by ferns, tree-ferns, calamites,
sigillarias, and lepidodendrons.
FIG. 130. CARBONIFEROUS FERNS The great importance of each
AND CYCAS-FERNS of these plants justifies a brief
A. Odontopteris subcuneata; B. Neuropteris Hpsrr infirm
cordata-, c. Eletkopteris longhitica; D. ueSCnptlDn.
Dictyopteris obliqua; E Phyllopteris anti- Impressions of leaVCS Very
qua; E'. Natural size (of E); F. Neuropteris J
cyclopteroides. Species from eastern Canada, like those of modem femS have
From Dawson, "Acadian Geology" . f , . ,
been found in great numbers
in the Coal Measures. Until quite recently these leaves were
believed to represent true ferns; it is now known, however,
that some of them bore seeds, and therefore are to be con-
sidered as gymnosperms. Palaeobotanists suspect that others
of these fern-like plants, in which seeds have not actually
been found, are likewise to be ascribed to the gymnosperms.
THE CARBONIFEROUS PERIOD 259
The fern-like leaves, therefore, belong either to ferns proper
or to fern-like plants actually or probably bearing true seeds,
and known by the very appro-
priate name Cycadofiliacales, or
cycas-ferns, in allusion to their
intermediate position between
the ferns and the lowest gym-
nosperms, the cycads. Hymeno-
phyllites from the eastern coal
fields is probably a true fern:
the cycas-ferns will be con-
sidered under the gymnosperms.
Giant ferns with leaves sup-
ported on a trunk like a tree FIG. 131. CARBONIFEROUS
were of common occurrence in TREE-FERNS
the forests of both Devonian and Carboniferous time. They
are known as tree-ferns, and are represented by Psaronius
and several other genera from our rocks.
Calamites are very closely allied to the common horsetail,
which may be found growing on wet, sandy soil to a height
of about eighteen inches in many parts of Canada. The
calamites, however, reached the dimensions of trees, with a
diameter up to fifteen inches, and had a large central pith
surrounded by an external zone of woody tissue. Narrow
vertical fluting is characteristic of both the inside and the
outside of this woody cylinder. At irregular intervals the
continuity of the fluting is interrupted by "nodes," from
which arise whorls of limbs. A great many species of calamites
are known: Dawson records nine from the coal fields of
Nova Scotia alone.
In addition to the calamites which have been determined
from stems, a considerable number of related forms have
been identified from foliage, e.g. Asierophyllites and Annularia.
The sigillarias were trees that grew to a height of 100 feet
or more, and played an important part in the formation of
coal beds. They were evergreen, spore-bearing trees, re-
markable in having two kinds of spores, some very large and
others very small. The trunk was rather ungraceful, with a
diameter as great as six feet at the base; it terminated in a
blunt point, and very rarely bifurcated or branched. Leaves
260 ELEMENTARY GEOLOGY
sprang in a regular manner from the whole surface of the
tree, but with advancing age and size the lower leaves fell
off, leaving scars on the bark. As these scars resemble seals,
the plant has been called the "seal-tree" or Sigillaria (sigilla,
a seal). The bark was marked by pronounced fluting, with
the leaf-scars arranged in parallel rows down the trunk.
Botanically, the plant is related to the existing lycopods.
Lepidodendron resembles Sigillaria in many ways, and like
it is related to the lycopods as represented by the existing
club mosses and ground-pines of our woods. The trees were
tall and graceful, with slender, gradually tapering trunks and
branches which arose by regular bifurcation. The leaves,
FIG. 132. CARBONIFEROUS TREES
i. Bark of Sigillaria; 2. Bark of Lepidodendron.
generally small and elongated, sprang from the whole surface
as in Sigillaria, and left scars in a similar manner. The bark
was not fluted as in Sigillaria, and the large, diamond-shaped
scars instead of being in vertical rows were arranged in a
spiral manner around the stem. The smaller branches bore
cone-like structures at their extremities, from which enormous
numbers of spores were produced.
Many species of both Lepidodendron and Sigillaria are
known from the Carboniferous rocks of eastern Canada;
also, in the under-clay are found numerous roots, to which
the name Stigmaria is given.
The gymnosperms are represented by the Cycadofiliacales,
already referred to, and the Cordaitales, which show relation-
ships to the conifers.
THE CARBONIFEROUS PERIOD 261
The Cycadofiliacales are well represented in the coal fields
of Nova Scotia: common examples are Alethopteris, Neuro-
pteris, and Sphenopteris. The "fern-ledges" near St. John,
N.B., have also yielded a large number of similar forms.
The Cordaitales were the most important gymnosperms
in Carboniferous time, and they may be considered as the
dominant type of gymnosperm in the Palaeozoic era. These
trees are related on the one hand to the cycads and on the
other to the more primitive conifers. The wood resembles
that of the araucarian conifers, but, unlike the true conifers,
the leaves are remarkably large. The trees grow to a large
size, sometimes to over 100 feet in height and 10 feet in girth
at the base. They appeared in Devonian time and were well
represented in the Devonian rocks of eastern Canada; in the
Carboniferous period, as stated above, they reached their
maximum development and rapidly declined thereafter.
Cordaites and Dadoxylon are common genera in the Carboni-
ferous rocks of Nova Scotia and New Brunswick.
CARBONIFEROUS INVERTEBRATES
Carboniferous time witnessed many changes in the inver-
tebrate life ; the old Palaeozoic types, so long dominant, began
to give place to new orders of beings destined to reach a
remarkable development in the following era. Furthermore,
there are many distinctive features in the life of the time which
enable us to summarise its main characteristics and to make
a fairly clear comparison with the fauna of the Devonian.
The great groups of corals, trilobites, and nautiloids show a
marked decline ; the pelecypods, gastropods, and the new type
of cephalopod increase; crinoids and blastoids reach their
maximum development; protozoa spring suddenly to a
position of great importance; and the higher arthropods,
including many air-breathing forms, become a striking feature
of the life of the time.
The Acadian Carboniferous strata were deposited in a sea
which was quite distinct from the great mid-continental
ocean; in consequence, the fossils differ somewhat from the
more typical American forms. The strata of the Rocky
Mountain area are very poor in fossils, and the few that occur
are not well preserved. To the Canadian student, therefore,
262 ELEMENTARY GEOLOGY
Carboniferous invertebrates are of little practical value,
although their importance in general historical geology is as
great as ever.
The following list includes a few of the most characteristic
Carboniferous fossils:
PROTOZOA. These little unicellular organisms are repre-
sented by a great number of forms which, in places, form
whole layers of rock. Fusulina, a small spindle-shaped form,
is the most common example.
CORALS. Of the Devonian genera many are extinct, but some
survive, particularly Diphyphyllum. The most characteristic
form, however, is Lithostrotion, a
compound coral having a rod-like
axis in the centre of each corallite.
Echinoderms. Crinoids and blas-
toids reach their maximum develop-
ment. Of the former, the genera
are remarkably numerous; Platy-
FIG 133 THE TYPICAL CAR- • •
••"-" J Actinocrinus will serve as
se. One-fourth examples. Blastoids are at the maxi-
naturaisize. mum development and disappear
with the close of the period. Pentremites is the commonest
genus. For the first time sea urchins are important; they
differ from all modern forms in that the shell is composed of
more or fewer than twenty rows of plates. Melonites and
Archceocidaris are common examples.
BRACHIOPODS. These creatures, long dominant among the
shell fish, are still numerous, but in this period they begin to
yield to the molluscs which are destined to replace them in
the seas of later ages. Spirifer is still abundant, but the loop-
bearing types, Terebratula and Dielasma, are increasingly
important. The most characteristic of all the brachiopods is
Productus. In the Acadian Carboniferous Productus semi-
reticulatus, a cosmopolitan species, is common ; other examples
are Spirifer glabra and Dielasma sacculus.
BRYOZOA. A peculiar screw-like bryozoan, Archimedes, is
one of the most striking fossils of the period; it is entirely
confined to rocks of this age.
PELECYPODS AND GASTROPODS. Both these groups are
more strongly represented than before, but the majority of
THE CARBONIFEROUS PERIOD 263
the species belong to old types. More particularly in the case
of the former group, there is a significant admixture of new
forms heralding the great change to come. Euompkalus and
12
FIG. 134. CARBONIFEROUS MARINE INVERTEBRATES
i. Actinocrinus multiramosus, three-eighths natural size; 2. Platycrinus tricondactylus;
3. Melonites multiporus, three-eighths size; 4. Archimedes wortheni, three-fourths size;
5. Pentremites sulcatus, half size; 6. Pleurotomaria mississippiensis, half size;
7. Productus semireticulatus, seven-eighths size; 8. Dielasma sacculus, seven-eighths
•size; 9. Allorisma pleuropistha, half size; 10. Euomphalus pentangulatus ; n. Goniatites
lyoni, three-eighths size; 12. Myalina recurvirostris , three-eighths size; 13. Edmondia
trapeziformis,halt size; 14. Fusulina cylindrica, in rock.
Bellerophon are the commonest gastropods, and Schizodus and
Myalina' are typical pelecypods.
CEPHALOPODS. A few Orthoceras survive, and there are many
264
ELEMENTARY GEOLOGY
coiled nautiloids. The nautiloid type of cephalopod continues
to exist to the present, but it never again occupies a position
of importance. The most characteristic cephalopods are the
goniatitoids, with more strongly angulated sutures than in
the clymenoids of the Devonian.
TRILOBITES. Only one family, the Proetidce, remains: it is
represented by five genera, of which Phillipsia is the most
abundant.
THE HIGHER ARTHROPODS. The higher invertebrate
FIG. 135. CARBONIFEROUS ARTHROPODS
i. Prestwichia dance; 2. Phillipsia lodiensis; 3. Eophrynus prestwichii (spider) ; 4. Steno-
dictya (insect). After Handlirsch.
animals with jointed limbs reach a development hitherto
unknown. Among the aquatic forms the ostracods, phyllo-
carids, and phyllopods occur in abundance. Eurypterids
survive, and Prestwichia is a very characteristic related form.
Spiders, scorpions, and myriopods occur in abundance, and
there is a remarkable development of insects: these belong
mostly to the types with straight or net-veined wings, and
sometimes measure more than two feet from tip to tip of the
THE CARBONIFEROUS PERIOD 265
wings. Haplophlebium barnesii, a form with seven inches'
expanse of wing, was found in the Carboniferous rocks of
Cape Breton.
CARBONIFEROUS VERTEBRATES
FISH. The armoured fish of the Devonian disappear with
its close, and the crossopterygian ganoids give place to another
type, in which the extremity of the vertebral column turns
up into the dorsal lobe of the tail and the paired fins are
without the scaly axis and marginal fringe. A family of these
fish, the Palceoniscidce, reached a position of pre-eminence; it
is represented by numerous species in the Carboniferous rocks
of the world, and by at least five from the Lower Carboniferous
FIG. 136. WING OF HAPLOPHLEBIUM BARNESII
A Canadian Carboniferous insect. From Dawson, "Acadian Geology."
rocks of New Brunswick. Rhadinichthys alberti, a small fish
from the Albert shales of New Brunswick, is the best known
Canadian form.
In addition to the Palceoniscidce, the Carboniferous fish
fauna consists chiefly of a few survivals of crossopterygians
and many lung-fishes and sharks.
AMPHIBIA. The lowest air-breathing vertebrates are known,
on the evidence of footprints only, from the Devonian rocks.
In Lower Carboniferous time these impressions are more
numerous, and in the upper part of the system not only
footprints, but actual skeletons have been found. These
animals are all small, not exceeding three feet in length;
they are mostly salamander-like, but legless, eel-like forms
are known as well. Many years ago a number of imperfect
skeletons of these primitive amphibians were found by Sir
William Dawson at the South Joggins, Nova Scotia. Prior to
FIG. 137. CARBONIFEROUS FISH
Rhadinichthys alberti, Albert shales of New Brunswick; 2. Cheirodus granulosus, Scotland;
3. Eurynotus crenatus, Scotland; 4. Pleuracanthus gaudryi, France. No. i seven-
eighths natural size, after Lambe ; Nos. 2 and 3 reduced, after Traquair ; No. 4 reduced,
after Brongniart.
THE CARBONIFEROUS PERIOD 267
these discoveries, in 1841, Sir William Logan recorded the
occurrence of footprints at Horton Bluff — the first evidence of
Carboniferous air-breathing vertebrates found in the world.
Exclusive of footprints, at least seventeen species of Amphibia
were described by Dawson and the great English palaeontol-
ogist, Owen, from the Carboniferous rocks of Nova Scotia.
For the Canadian student no better examples of Carbon-
iferous amphibians could be cited than those illustrated in
FIG. 138
i. Restoration of Carboniferous landscape in Nova Scotia, showing primitive amphibians;
2. Erect trunk of Catamites in which the bones of some of the amphibians were found.
From Dawson, "Acadian Geology"
Figure 138, a reproduction of Dawson's original woodcut,
published in 1878.
REPTILES. It has long been a matter of dispute whether
or not true reptiles appeared in Carboniferous time. Professor
Williston now holds the opinion that a single skeleton, lacking
the skull, is the only known representative of Carboniferous
reptiles. The remains were found at Linton, Ohio, in Upper
Carboniferous rocks, and have been given the appropriate
name Eosauravus.
Not much is known of conditions on the dry land during
the Carboniferous, but in eastern Canada, as in many other
parts of the northern hemisphere, there were vast marshy
268 ELEMENTARY GEOLOGY
forests in the lowlands with rank, almost tropical, growths.
Air-breathing inhabitants were numerous, and the life was
varied, for Sir William Dawson has shown that there were
little snails feeding on the fern leaves, myriapods burrowing
in decaying tree- trunks, many insects flitting among the
trees, and scorpions and spiders on the look-out for them.
Even the vertebrates, in the form of little amphibians, crept
up the tree- trunks and rested in hollow stumps; so that the
lowlands, at least, displayed a varied and interesting life.
Judging by the coal plants found even within the Arctic
Circle in the great northern islands of Canada, the climate
and the life seem to have been uniform all over the world.
CHAPTER X
THE PERMIAN PERIOD
THIS system receives its name from the province of Perm in
Russia, where it is well developed. In Europe the rocks of
the system rest conformably or unconformably on the under-
lying Carboniferous strata. In North America no structural
break marks the upper limit of the Carboniferous; in con-
sequence, the Permian system is ill denned: it fades im-
perceptibly into the Upper Carboniferous or Pennsylvanian,
and in the opinion of American geologists is not worthy of
being considered a great system.
PHYSICAL EVENTS OF THE PERMIAN IN
NORTH AMERICA
The shallow seas of Upper Carboniferous time had begun
to retreat before the close of that epoch, and by the middle
of the Permian they had withdrawn almost entirely from the
present area of the continent: in consequence, no marine
strata were deposited over regions now accessible, and we have
no record of sedimentation for Upper Permian time in North
America. In other parts of the world, however, notably in
South Africa, a continuous record is available which fills in
the gaps that would exist in geological history were North
America to be relied on to tell the whole story.
We have already seen that much volcanic activity was
manifested in the Pacific Coast region during the Upper
Carboniferous ; this state of unrest continued into the Permian
and may be regarded as the warning of great events to come,
for one of the most profound disturbances that have affected
the earth's crust occurred toward the close of Permian time.
We have seen that the continent had been sufficiently uplifted
to drain off the seas by the middle of the period. This upward
movement continued through the closing stages of the
269
270 ELEMENTARY GEOLOGY
Permian, and was manifested with such intensity in eastern
North America that the Appalachian mountains were elevated,
the terrestrial strains relieved, and the continent prepared
for another cycle of erosion. To this great event the name
Appalachian revolution is given: with it the old order of
things closes and the Palaeozoic era ends.
THE PERMIAN IN OTHER CONTINENTS
Hitherto the geological history of the world can be fairly
well illustrated by using North America as an example. The
conditions in Permian time, however, were so varied in
different parts of the globe that general deductions cannot
be drawn from the history as revealed by the rocks of
this continent.
In western Europe the Permian rocks are chiefly con-
glomerates, sandstones, and shales of a prevailing red colour.
The red colour, the paucity of fossils, and the occurrence of
beds of gypsum indicate deposition under desert conditions.
The strata are usually unconformable with the underlying
Carboniferous, and seem to have been rapidly deposited in
isolated basins. Passing westward into European Russia and
thence into Asia, Permian rocks are found over wide areas;
they are truly marine deposits with a rich pelagic fauna.
In the southern hemisphere very different conditions seem
to have prevailed. North of the equator, in India, there is a
great accumulation of sediments of freshwater origin known
as the Gondwana system, including strata varying in age from
Carboniferous to Middle Mesozoic. The Permian system as
recognised in Europe is not to be distinguished, but the lower
part of the Gondwana is roughly correlated with it and is
called Permo-Carboniferous.
In South Africa the great Karoo formation, covering thou-
sands of square miles, is comparable in age, in fossils, and in
conditions of sedimentation with the Gondwana of India.
In Australia, resting on true Carboniferous rocks, is a series
of strata also ascribed to the Permo-Carboniferous. These
rocks are coal- bearing and show a flora comparable with
that of India and South Africa; in this case, however, strata
THE PERMIAN PERIOD 271
of marine origin are associated with the fresh or brackish
water deposits. In South America, also, the characteristic
plants of the Gondwana system are found in strata ascribed
to Permo-Carboniferous age.
On account of the striking similarity in the plant life
of these regions, and for other reasons, many geologists
believe that Asia, Africa, Australia, and South America
were united into a great transverse continent, to which the
name Gondwana Land has been given.
A most remarkable feature, common to all the regions
mentioned above, is the occurrence of great beds of boulder
clay, filled with striated stones and resting on a striated
surface of the underlying formations. The lowest formation
of the Karoo series of South Africa, the Dwyka, is of this
nature; the Talchir conglomerate at the base of the Gond-
wana of India is similar; and the Permo-Carboniferous de-
posits of Australia and South America present the same
interesting feature.
In view of these facts, geologists are now agreed that an
extensive glaciation affected the southern hemisphere and
even reached north of the equator in Permo-Carboniferous
time — a glaciation exceeding that of more recent times in
the northern hemisphere. To this great event the name
Permo-Carboniferous Ice Age is given.
If the geological history of South Africa and Australia had
been written before that of Europe and North America, the
great divisional lines would have been drawn at different
levels. Instead of the Australian geologists having to use
such terms as Permo-Carboniferous, we should be struggling
with hyphenated words derived from great systems estab-
lished by our antipodean cousins.
THE PERMIAN SYSTEM IN CANADA
Permian strata are of comparatively small extent in Canada;
two or possibly three areas may be recognised, as follows:
i. ACADIAN AREA. Conformably overlying the* Coal
Measures is a series of reddish sandstones and shales,
sometimes with thin seams of coal. The rocks occur in Nova
272 ELEMENTARY GEOLOGY
Scotia along the shores of Northumberland strait and form
the whole of Prince Edward island. The prevailing red
colour of the rocks and soils, together with the deep green of
the vegetation, gives a very characteristic appearance to the
scenery of the island. The better grades of sandstone are used
for building, and the shales for brick-making. That these
rocks are to be exactly correlated with the Permian of Europe
is not established; they are not separated by any physical
breaks from the Coal Measures and do not contain conclusive
marine fossils. In consequence, the term Permo-Carboniferous
is less liable to create a false impression.
2. ROCKY MOUNTAIN AREA. In the mountains of southern
Alberta, the hard Rocky Mountain quartzite of the Carboni-
ferous is covered by dark-coloured shale containing many
hard bands. This formation is not exposed on the summits
of the eastern ranges, as it has been removed by erosion. On
the back slopes, however, it is found in the lengthwise valleys,
as near the Banff Hotel on the line of the Canadian Pacific
Railway. It is to be noted that some authorities consider
these shales to be of Triassic rather than of Permian age.
3. PACIFIC COAST AREA. It is generally thought that the
mixed sedimentaries and volcanics of the coast region which
we have ascribed to the Upper Carboniferous may contain
also strata of Permian age.
LIFE OF THE PERMIAN
The life of Permian time, regarded in a broad way, shows a
continuation of the Carboniferous types, both animal and
vegetable, with an increasing admixture of the newer life
which is to become dominant in the next era. The outstanding
features are the unique Glossopteris flora of the Gondwana
and the development of air-breathing vertebrates.
PLANTS. Of the numerous Carboniferous plants, many
species survive into the Permian; other species, and even
genera, become extinct with the close of the Carboniferous.
Perhaps the most significant difference is the profusion
of cycads, a type of life which became dominant in the
later Mesozoic era.
THE PERMIAN PERIOD
273
The remarkable Glossopteris flora consists of numerous
closely related ferns, which developed under the conditions of
cold climate which prevailed in the southern
hemisphere. The plants were hardy and
remarkably cosmopolitan, for identical
species have been found in India, Africa,
and South America.
INVERTEBRATES. A very impoverished
fauna is found in the Permian strata of
western Europe, and the Permo-Carboni-
ferous rocks of Canada are almost destitute
of the remains of marine organisms. The
Permian strata of Russia, however, yield an
abundant fauna, on which must be founded GLOSSOPTERIS FLORA
any general remarks on the invertebrate Glossopteris browniana.
life of the period. This life is strikingly ^terzittd.
like that of the Carboniferous, and shows the same tendencies
in a more accentuated form. For instance, the eurypterids
have disappeared, the trilobites have dwindled still further,
and the ascendancy of the molluscs over the brachiopods,
and of the gohiatitoids over the nautiloids, is more
marked. The crinoids, so abundant in the Carboniferous,
FIG. 140. PERMIAN AMPHIBIAN
Archegosaurus dechini. From Zittel after H. von Meyer.
show a remarkable decline, as their remains are rare in
Permian rocks.
FISH. The fish fauna of the Permian is very similar to that
of the Carboniferous, with the Paiaoniscidcz predominating:
sharks and lung-fishes are also abundant. The genus Palceo-
niscus is confined to the Permian.
AMPHIBIANS. The Permian, together with the succeeding
274
ELEMENTARY GEOLOGY
Triassic period, is characterised beyond all else by the great
development of amphibian life. The amphibians of to-day
are small creatures like the common frog, and play but a
subordinate part in the life of the time; in the Permian they
were large creatures and exercised dominion over the animal
life of the period.
These early amphibians differ from frog-like creatures in
that the bones of the side of the head are continuous, and not
opened up as in the frog; on this account they are called
Stegocephalia, or "plated cheeks." Some of them, also, have
the enamel of the teeth enrolled in a peculiar manner, which
FIG. 141. PERMIAN REPTILE
Dimetrodon incisivus. About one-twenty-fifth natural size. From Case,
" Pelycosuuria of North America."
gives a very complicated appearance to a cross section;
hence the name Labyrinthodontia, or "labyrinth-toothed."
Of the numerous Permian stegocephalians, Branchiosaurus
and Archegosaurus may be cited as examples. The former is
a small type covered above and below with an armature of
small hard scales; the latter is a fairly large European type
of labyrinthodont, and is represented in America by a similar
form, Eryops.
REPTILES. The great ascendancy to be enjoyed by reptiles
at a later date is foreshadowed in Permian time, for not only
are they numerous, but give evidence of adaptation to various
modes of life. Water, marsh, and land-dwelling forms are
THE PERMIAN PERIOD 275
known, and even types adapted to an arboreal existence. The
Lower Permian beds of Texas have yielded many skeletons,
and the Karoo formation of South Africa is famous for the
number and variety of its reptilian remains. Pareiasaurus is
a large, amphibian-like, massive, land-dwelling reptile from
the Karoo; Dimetrodon and Ar&oscelis are examples of the
Permian reptiles of Texas. Aquatic types are represented by
numerous small forms from South Africa and South America,
e.g. Mesosaurus.
The Permian seems to have been a time of stress for the
inhabitants of the world, great ice sheets and also great
deserts taking the place of the mild monotony of the Car-
boniferous. This probably accounts for the great changes
taking place in the vertebrates.
CHAPTER XI
SUMMARY OF THE PALAEOZOIC ERA
IN previous chapters we have become acquainted with the
great events of the long periods extending from the opening
of the Cambrian to the close of the Permian, and which
together constitute the Palaeozoic era. The Cambrian opened
with a continent of unknown extent on which successive
layers of rock, some here, some there, were laid down in seas
which invaded the land one after the other throughout the
whole era. The successive floodings and retreats have been
made use of to define the periods. In some cases the rocks of
the different systems are separated by strong unconformities,
in others there is scarcely a perceptible break between
successive systems.
While terrestrial movements were going on gradually
throughout the whole era, certain times were marked by
upheavals of such magnitude as to deserve the name of
revolutions. The more important of these, all of which were
manifested much more strongly on the eastern side of the
continent, were the Taconic disturbance at the close of the
Ordovician period, the movements accompanied by volcanic
activity at the close of the Devonian, and the great Appala-
chian revolution which brought the era to a close.
Wide-spread seas and consequent great formations were
characteristic of the Ordovician ; minor oscillations and more
local formations characterised the latter part of the era.
Physical events during the Palaeozoic were not essentially
different from those of earlier and of later time, and there is
nothing in their nature particularly characteristic of the era:
it is to the life history that we must look for a means of
defining the Palaeozoic.
The era, as the name implies, is essentially the time of
"ancient life," a time in which all the creatures were very
different from those now inhabiting the globe. Nearly all
276
SUMMARY OF PALEOZOIC ERA 277
the great classes of organisms, with the exception of the
flowering plants, birds, and mammals, had at least some
representation. Among the plants, the sea weeds and vascular
cryptogams were predominant; invertebrate groups entirely
confined to the era are graptolites, stromatoporoids, cystids,
blastoids, trilobites, and eurypterids; other invertebrate
groups, prominent but not exclusively Palaeozoic, are bryo-
zoans, brachiopods, and nautiloids. Vertebrates are repre-
sented by archaic fish, and towards the close of the era by
amphibians and reptiles.
CHAPTER XII
THE MESOZOIC ERA— THE TRIASSIC PERIOD
IN previous chapters we have followed the great events of the
long Palaeozoic periods; we have seen how the. ever- restless
seas have flooded and ebbed, always leaving a rock-written
record, the pages of which have been pieced together to make
the history of Palaeozoic time. We have seen that this history
is continuous, although we have failed to find all the pages,
and we have made use of physical disturbances and faunal
changes as punctuation marks for our story, or in other
words, to divide the era into periods and epochs. In entering
upon the consideration of another great era it is well to keep
in mind this continuity of geological history. Let us carefully
avoid the conception of the Mesozoic as a new age marked off
from the Palaeozoic by some tremendous catastrophe. Let
us regard it, rather, as a continuation of the story, a new
chapter written under different conditions, but fading in-
sensibly into the previous one. It is true that an unrecorded
interval makes the division a very real one in some parts of
the world, but it is equally true that there is absolutely no
observable break between the two groups of rocks in others.
Our study of the Palaeozoic periods has shown us that the
rise and fall of races of organisms furnishes evidence of the
utmost importance towards the orderly arrangement of our
story into convenient chapters. The races of the Palaeozoic
appeared, reached a maximum, and in some cases declined
and fell, but the process was gradual and extended over
millions of years. The same conception of gradual change
must be applied to the life of the Mesozoic as compared with
that of the Palaeozoic. In a broad way there is a great differ-
ence between the faunas and floras of the two eras, but nearly
all the great races characteristic of Mesozoic time had their
inception in the latter part of the Palaeozoic; on the other
hand, some races essentially Palaeozoic lingered on into
Mesozoic time. Reptiles, amphibians, ammonites, and cycads,
278
THE MESOZOIC ERA 279
the dominant races of Mesozoic time, had all appeared before
the close of the Permian, and the occurrence of Orthoceras in
Triassic rocks attests the survival of a purely Palaeozoic type
into the lower part of the Mesozoic.
The Mesozoic, or era of " middle life," is divided by European
geologists into three periods : Triassic, Jurassic, and Cretaceous.
American geologists are now inclined to recognise four periods :
Triassic, Jurassic, Comanchian, and Cretaceous. A general
account of the physical, faunal, and floral characteristics of
the era as a whole can be better understood after the periods
have been considered : such a description is deferred, therefore,
to Chapter XV.
THE TRIASSIC PERIOD
In Germany, where the rocks of this system were first
studied, the strata may be distinctly arranged in three series:
on this account the system was named Triassic. Names based
on local peculiarities are generally found to be unsatisfactory,
and the present instance is no exception, as a three-fold
division of the rocks of the system is not observed in other
parts of the world. The rocks of the type locality are largely
of continental origin, and it has become customary to dis-
tinguish this facies as the German Triassic. On the other
hand, the Triassic strata of the Alps are distinctly of saltwater
origin; in consequence, the marine facies of the system is
called the Alpine Triassic.
PHYSICAL EVENTS OF THE TRIASSIC IN
NORTH AMERICA
The elevation which resulted from the Appalachian revolu-
tion left the eastern shore of the continent farther out to sea
than at present ; in consequence, any marine strata that were
formed off the coast are still hidden beneath the waters of the
ocean. Faulting and other terrestrial disturbances affected
the eastern border region, with the production of gradually
rising sections separated by narrow troughs or valleys. In
these valleys were deposited coarse and rapidly accumulated
28o ELEMENTARY GEOLOGY
sediments derived from the decay of the neighbouring land-
masses. The Triassic rocks of eastern North America, there-
fore, are distinctly of non-marine or continental origin. The
state of unrest indicated by the extensive faulting of the time
naturally facilitated igneous activity, with the result that
many sills and flows of dark, basic rocks are associated with
the sedimentaries. The close of Triassic time was marked in
this area by a considerable elevation which affected the region
to the east of the Appalachian mountains.
On the western side of the continent the waters of the
Pacific ocean advanced over a wide area, and at the same
time there was a tremendous manifestation of volcanic
activity. All along the continental shelf, from California to
Alaska, the Triassic sedimentaries are mingled with effusive
and fragmental rocks of volcanic origin. A pronounced
elevation accompanied by much folding of the rocks brought
the Triassic period to an end in the Cordilleran region. This
event was more profound in Alaska, but its effects were felt
far to the south: it has been called the Chitistone disturbance
by Schuchert.
THE TRIASSIC SYSTEM IN CANADA
Only in the extreme east and west of the Dominion are
Triassic rocks known: they may conveniently be described
under two areas:
i. NOVA SCOTIA AREA. The sedimentary rocks of this age
are chiefly soft, friable sandstones, often associated with beds
of gypsum. They occur on the shores of Minas basin and
eastward to beyond Truro, also on Annapolis bay, and near
Quaco on the New Brunswick side of the Bay of Fundy. These
rocks rest with profound unconformity on the underlying
strata, and were deposited in one of the narrow troughs which
we have already seen to be characteristic of the physical
geography of eastern North America in Triassic time.
Of greater importance than the sedimentaries are the flows
of igneous rock, which in their more solid phases are dark-
coloured diabases. Associated with these massive rocks are
less compact, amygdaloidal flows of grey, green, red, or purple
THE MESOZOIC ERA
281
colour. The whole south-east coast of the Bay of Fundy, from
the extremity of the neck of Digby to Cape Split, is bordered
by rocks of this kind; they also occur on the north shore of
Minas basin and on Grand Manan island.
Many of the more massive flows show to perfection the
columnar jointing so characteristic of volcanic rocks. This
feature adds to the beauty and interest of a strip of bold and
FIG. 142. TRIASSIC TRAPS OF NOVA SCOTIA, CAPE BLOMIDON
From a photograph by Professor Clarkson, Wolfville, 7V.S.
picturesque coast which is in pleasing contrast to the prevailing
mud flats of much of the Fundy shore.
The amygdules or almond-shaped cavities in the less massive
flows in many cases have been filled with secondary minerals,
particularly varieties of silica and zeolites. The disintegration
of -the rock sets free the harder substances which are often
found in the form of pebbles at the base of the cliffs. Agate,
moss agate, chalcedony, and amethyst, frequently of great
beauty and decorative value, are to be obtained at many
points along the coast.
2. BRITISH COLUMBIA AREA. Before describing the Triassic
282 ELEMENTARY GEOLOGY
rocks of this region it is advisable to review briefly the events
which we have already considered. We have seen that a
Pre-cambrian landmass existed in central and western British
Columbia, that the Rocky Mountain geosyncline developed
to the east of this old land, and that through all Palaeozoic
time strata accumulated in this depression to an enormous
thickness. We have also seen that in the Upper Carboniferous
epoch the region to the west of the Selkirk and Columbian
mountains was depressed beneath the sea for the first time
and became a new region of sedimentation, to which the name
Western geosyncline is given.
In the Rocky Mountain geosyncline sedimentation con-
tinued into Permian time, but the disturbances at the end of
the Palaeozoic caused a temporary retreat of the sea, with the
result that no strata were made in Triassic time in southern
British Columbia. Authorities are not agreed on this point, as
some ascribe the Upper Banff shale to the Triassic. Farther
north, however, on the Peace river, undoubted marine
Triassic rocks occur.
Over a wide region of the Western geosyncline sedimentary
and volcanic rocks were deposited on the old Pre-cambrian
floor in the Upper Carboniferous. It is possible that this
condition continued into the Permian, but rocks of this age
are doubtful and we may conclude that the Permian was
largely a time of uplift and erosion in the western geosyncline.
Triassic time, however, witnessed a second wide-spread de-
pression in the region of the Western geosyncline and a
deposition of sediments on the eroded surface of the Upper
Carboniferous rocks. The Triassic sedimentaries, however,
are insignificant in amount when compared with the great
volume of igneous matter extruded during the period. From
fissures in the earth's crust, and less frequently from volcanic
craters, enormous masses of basalt and diabase were mingled
with the sedimentaries. To the whole complex of igneous and
sedimentary rocks the name Nicola series has been given; in
places this series is 13,500 feet thick and consists, to nine-tenths
of its volume, of igneous rocks.
A subsequent event, the formation of the Coast Range, has
divided the region of the Western geosyncline into two great
north-and-south belts. Both Carboniferous and Triassic rocks,
THE MESOZOIC ERA 283
therefore, are to be found in two general regions of the old
Western geosyncline — the central interior and the islands of
the Pacific coast.
Although the copper, gold, and silver ores of southern
British Columbia were formed at a later time, they frequently
occur in association with the igneous rocks of Carboniferous
and Triassic age. The Triassic limestones of the southern
end of Texada island in the Strait of Georgia yield a very
handsome red variegated marble.
LIFE OF THE TRIASSIC
PLANTS. The ascendancy of vascular cryptogams ends with
the Palaeozoic, for the life of the Triassic period shows a great
increase in the gymnosperms as represented by conifers and
more particularly by cycads. As these trees were destined
to become dominant in the later periods of the Mesozoic, we
have in the Triassic a time of change, an interregnum between
the reigns of the cryptogams and the gymnosperms, with the
new type already ascendant.
The great lepidodendrons and sigillarias had practically
disappeared, but the calamites were represented by quite
numerous species still of large size, but more closely related to
the modern horsetails than Calamites itself. Ferns of new
genera were also fairly abundant. Cycads with great green
leaves (Pterophyllum) and the small-leaved, araucarian-like
conifers (Voltzia) ruled the vegetation, at least of the higher
lands, and imparted to the forest landscape of the time a
somewhat gloomy and monotonous appearance.
The known species of Triassic plants are very numerous,
and more than a third of these are American. The Triassic
strata of Virginia have yielded the most abundant remains.
INVERTEBRATES. The continental character of many of the
Triassic sediments and the mingling of others with volcanic
rocks have not favoured the preservation of marine fossils.
Although the fauna, on the whole, is rather scanty on this
account, nevertheless in regions of marine sedimentation,
where the Alpine type of Triassic rock was formed, fossils of
marine invertebrates are not wanting. The Palaeozoic type of
284
ELEMENTARY GEOLOGY
coral has disappeared and its place is taken by a new race,
the Hexacoralla, which has persisted to the present day. The
decline of the brachiopods is pronounced, and their position
is now subservient to that of the molluscs. The newer type
of pelecypod which began to make its presence felt in Per-
mian time is now firmly established and is represented by
such genera as Pecten and Myophoria. Gastropods, while
a little behind the pelecypods in development, are repre-
sented by new forms with which are mingled survivals
of Palaeozoic types.
Among the molluscs, the cephalopods show the most striking
changes. The old nautiloid type is almost extinct, and the
FIG. 143. TRIASSIC INVERTEBRATES
i. Ceratites nodosus; 2. Encrinus liliiformis;
2, one-half size; 3,
3. Pecten valoniensis. i, natural size;
two- thirds size.
goniatitoids give place to ceratitoids and ammonitoids. We
have seen that the clymenoids of the Devonian and the
goniatitoids of the Carboniferous are distinguished by an
increasing angularity of the suture or line of union between
the partitions and the shell wall. The ceratitoids have folded
sutures with the backward turn of the fold crumpled; the
ammonitoids show a remarkable degree of complexity in the
folding of the suture. The amount of evolution accomplished
by these organisms in the Triassic was remarkable. Ceratites
is typically Triassic, andArcestes is a good example of the type
with highly developed sutures.
The echinoderms of the Palaeozoic have all passed away. No
cystids or blastoids are known in the Triassic, and the abundant
THE MESOZOIC ERA
285
Crinoids of the Carboniferous, decadent in the Permian, are
now represented by an incoming race of different type. In the
new type of crinoid the space
inside the arms is not plated but
is protected by a tough mem-
brane, and the arms are more
developed than in the Palaeozoic
forms. Encrinus liliiformis is a
very typical fossil of the time.
The modern kind of sea urchin
with twenty rows of plates re-
places the archaic type of the
Palaeozoic. Cidaris is the most
abundant Triassic sea urchin.
The higher crustaceans are
represented by the decapod
Pemphix.
FISH. The Triassic fish fauna
is not remarkable and bears a
strong resemblance to that of the
Permian. Heterocercal ganoids
and other ganoids of a higher
type were dominant. Sharks are
known by teeth and spines, and
the last of the marine lung-fishes
by numerous teeth of Ceratodus.
AMPHIBIA. These creatures
attained their maximum de-
velopment in this period, which
together with the Permian may be called the Age of Amphibia.
The labyrinthodont type of stegocephalian is particularly
abundant, and is represented by some forms of great size, e.g.
Mastodonsaurus, with a head a metre and a quarter in length.
REPTILES. We have seen that a remarkable development
of .reptilian life was a feature of the Permian; in the Triassic
this development continued to such a degree that the fore-
runners of all the great tribes of reptiles, except the snakes,
had appeared before the close of the period. The small reptiles
of the Permian seem to have had but a short term of existence,
for all the species, and in many cases the sub-orders to which
FIG. 144. TRIASSIC CRUSTACEAN
Pemphix sueurii. After Zittel.
286
ELEMENTARY GEOLOGY
they belong, had become extinct before the opening of
Triassic time.
A remarkable group of reptiles from the Karoo formation of
FIG. 145. TRIASSIC WATER REPTILE
Nothosaurus. From Williston, " Water Reptiles, Past and Present."
South Africa is the Theriodontia, or beast- toothed forms. These
animals show many anatomical peculiarities which suggest a
FIG. 146. PRIMITIVE TRIASSIC CROCODILE
Mystriosuchus. From Williston, " Water Reptiles, Past and Present."
mammalian relationship, and it is confidently believed by
many authorities that it was from these reptiles that the
THE MESOZOIC ERA
287
great race of mammals arose. Cynognathus is one of the most
typical examples.
The extraordinary sea-going reptiles which became so
abundant in the later periods of the Mesozoic, and which are
more fully described
on page 300, had their
beginning here. The
long- necked type is re-
presented by Notho-
saurus and primitive
examples of Plesio-
saurus, and the short-
necked type by primi-
tive ichthyosaurs.
True crocodiles had
not yet appeared, but
an archaic order known
is
as the Parasuchia
particularly character-
pic. 147. TRIASSIC VERTEBRATES
Upper figure, Anchisaurus colurus, one of the earliest
dinosaurs. Lower figure, Rutiodon manhattanensis,
a phytosaur or ancestral crocodile. After Lull and
Matthew.
istic of the Triassic.
These creatures are
crocodile - like, but
differ in the constant
possession of a long snout and in the position of the external
nostrils, which are placed far back near the eye, instead of
being situated at the end of the snout. Belodon, Mystrio-
suchus, and Rutiodon are typical examples.
The most extraordinary group of all the reptiles is that of
the dinosaurs, which will be more fully considered later. It
is interesting to note that the earliest examples of this great
race of land or marsh- dwelling reptiles are known from the
Triassic rocks. Anchisaurus is a form from Connecticut well
worthy of note. From Prince Edward island a related dino-
saur has been described under the name Bathygnathus borealis.
In addition to actual skeletons, the Triassic rocks
have yielded a remarkable number of footprints which
were the occasion of much speculation before the discovery
of distinct remains.
CHAPTER XIII
THE JURASSIC PERIOD
WHILE the term Triassic is of German origin, the Jurassic
period owes its name to Swiss and French geologists, by whom
the rocks of the system were studied in the Jura mountains.
If priority of name were strictly adhered to we should call
this system the Oolite, a name given to it at an earlier date
by the great English geologist, William Smith. As the
term Oolite refers to a structural peculiarity of some of the
rocks, it has been abandoned in favour of the name of
geographical origin.
The Jurassic is a great system which has been recognised
in many parts of the world, but the conditions of sedimenta-
tion were very different at different places, and distinct
changes are to be observed within limited geographical bounds.
The Jurassic formations are local in development, a condition
which seems to increase with the passage of geological time.
PHYSICAL EVENTS OF THE JURASSIC IN
NORTH AMERICA
Throughout Jurassic time a very large part of the present
area of North America remained out of water and conse-
quently was subject to profound erosion. Jurassic history is
written in North America only in the Pacific border region.
Early Jurassic time was marked by a marine invasion which
affected the coast arid islands in the northern part of this
district and farther south advanced over parts of California,
Oregon, and Nevada. In later Jurassic time a greater flood
from the north (Logan sea) advanced over a large part of
Alaska and British Columbia, extending as far south as the
state of Utah.
We have seen that a state of unrest existed in this area
during the Permian and Triassic, and that volcanic activity
was manifested on a large scale. Again, in the Jurassic vul-
288
THE JURASSIC PERIOD 289
canism was pronounced with a great outpouring of basic
lavas and other volcanic products along the continental shelf.
The period was brought to a close by a profound elevation
whereby the Cascade and other ranges of mountains were
formed. This event was accompanied by the most extra-
ordinary outburst of molten matter that has occurred since
the Pre-cambrian.
From Lower California to Alaska the pre-existing rocks were
torn open, invaded, and lifted up as remnants by enormous
upwellings of igneous magmas of an acid nature, which on
consolidation have resulted in rocks of a general granitic
aspect. These rocks in the form of multiple batholiths now
constitute whole ranges of mountains, e.g. a great range
in the Sierra Nevada mountains and the Coast Range of
British Columbia.
THE JURASSIC SYSTEM IN CANADA
It is evident from what has already been said that Jurassic
strata can appear only in the western part of Canada. Owing
to the inaccessible location of much of the northern region, in
which Jurassic rocks are thought to occur, the limits of the
system have not yet been worked out in detail. The known
occurrences may be roughly divided into four areas as below:
i. ROCKY MOUNTAIN AREA. We have seen that the Rocky
Mountain geosyncline continued to be an area of deposition
until the close of Permian time, that the sea was partially
withdrawn during the Triassic, and that it returned in the
latter half of the Jurassic period. The upward and downward
movements whereby these changes were effected must have
been of a broad and gentle character, for the Jurassic strata
rest with scarcely a disconformity on the Upper Banff shales
of the Permian.1 These rocks consist entirely of shales and
constitute a formation known as the Fernie, which reaches
in places a thickness of 1500 feet. The strata are fossiliferous
and contain an abundance of ammonites and belemnites in
1 The apparent conformity of the Upper Banff shales with the over-
lying Fernie beds has been used as an argument in favour of the
Triassic age of the former. See pages 280 and 282.
T
2go ELEMENTARY GEOLOGY
places. Exposures are best seen in the valleys between the
more easterly ranges. The rocks doubtless originally extended
across the whole area occupied by these ranges, but since the
uplift of the mountains they have been removed by erosion
from the summits of the ranges. The eastward extension
of the Fernie shale is proved by its occurrence, but with
greatly diminished thickness, in the foothills east of the
main mountains.
2. INTERIOR BRITISH COLUMBIA AREA. The broad region
lying between the Columbian mountains and the Coast Range
constitutes the interior plateau area of British Columbia. In
the southern part of this belt sedimentary strata of Jurassic
age are doubtful; but farther north, along the line of the
Grand Trunk Pacific Railway, the Hazelton formation contains
fossils which attest its Jurassic age. The rocks are chiefly
tufaceous sandstones and dark-coloured shales, which indi-
cate that continental accumulations were mingled with marine
deposits in building up the beds.
3. YUKON AREA. Near the Alaska boundary and at other
points in the far north sedimentary strata are found which
are probably to be ascribed to the Jurassic system.
4. COAST AND ISLANDS AREA. Jurassic rocks, chiefly
argillites and limestones, occur on Vancouver island, Texada
island, Queen Charlotte island, and other islands of the
Pacific coast. In all cases they are much cut by volcanics
and frequently interbedded with fragmental and extrusive
rocks of igneous origin. The whole complex reaches a
thickness of several thousand feet, and is referred to as the
Vancouver group.
The association of the limestones with volcanic rocks has
rendered them crystalline in structure: they are quarried for
lime and cement-making, for use in the pulp mills, and for
flux in metallurgical operations;
THE JURASSIC IGNEOUS ROCKS OF BRITISH COLUMBIA
During this period igneous activity was not shown in the
region of the Rocky Mountain geosyncline; in consequence,
the Fernie shale of this section is not associated with volcanic
rocks. On the other hand, all the Jurassic rocks of the islands
THE JURASSIC PERIOD
291
are cut by dikes, covered by flows, and intermingled with
fragmentaries. The most abundant volcanic rocks are ande-
sites and andesite porphyries, but the more basic rocks, such
as basalt, are not infrequent.
Of greater importance are the immense masses of grano-
diorite and related rocks, which in the form of batholiths
appeared at the close of Jurassic time. For more than a
FIG. 148. SKETCH MAP OF BRITISH COLUMBIA
Showing the Coast Range batholith, the Nelson batholith, and other smaller masses of granite
or related rocks. The Coast Range is not indicated on the Alaskan side of the boundary.
thousand miles along the coast, with a width varying from
30 to 1 20 miles, stretches the great Coast Range of mountains,
which is made up entirely of these rocks. The appearance of
this range marks a great change in the topography of British
Columbia, for the region of the Western geosyncline is now
cut into two.
Other less extensive but very large batholiths of grano-
diorite, some of which may be of slightly later age, occur at
several places in British Columbia: most important of these
292 ELEMENTARY GEOLOGY
are the batholiths of Vancouver island and of Nelson, in the
southern part of the province.
The rocks of the Coast Range and of the Nelson batholith
are extensively quarried for building purposes. The stone is
a grey to pink granodiorite, and it has been used for some
of the finest structures in Victoria, Vancouver, and other
western cities.
LIFE OF THE JURASSIC
In favoured localities the life of Jurassic time was exceed-
ingly abundant and varied. The new type of life which was
foreshadowed in the Permian and became ascendant in the
Triassic now reaches a remarkable development. The varied
conditions of sedimentation, marine, brackish, and freshwater,
has permitted the preservation of a correspondingly varied
fauna and flora, and the favourable character of many of the
sediments has made possible the entombing of organisms of
the most delicate structure.
The outstanding features of Jurassic life are :
(i) The dominance of cycads and conifers.
(a) The profusion of gastropods and pelecypods.
(3) The extraordinary development of ammonites and
belemnites.
(4) The ascendancy among the fish of the " shining- scaled
ganoids."
(5) The number and variety of reptiles.
The great development of Jurassic strata in Europe, the
excellent preservation of the fossils, and the accessibility of
the exposures have all contributed to the knowledge of these
remains, of which about 15,000 species are known. In North
America, as we have already seen, nearly all these favourable
conditions were absent. Most of the continent was out of
water all through Jurassic time, and the areas in which
sedimentation did take place were subject to both contem-
poraneous and subsequent vulcanism. As a result of these
conditions the Jurassic strata of North America have yielded
a flora and fauna insignificant when compared with those
of Europe.
In Canada the Fernie shale is fossiliferous in places, and
THE JURASSIC PERIOD
293
some of the layers of the Vancouver group in Queen Charlotte
island have yielded many fossils. In both cases, however,
the fossils are badly preserved and are frequently pressed flat.
Of the great reptiles the Canadian Jurassic rocks have yielded
no recognisable examples, although a few disconnected bones
have been found. In the description of Jurassic life it is
FIG. 149. MESOZOIC PLANTS
Figures i to 6, cycads; Figures 7 and 8, conifers, i. Stem of Cycadoidea superba, South
Dakota; 2. Leaves of Zamites feneonis, France ; 3. Leaves of Otpzamites beani, England ;
4. Leaf of Nilssonia pplymorpha (Triassic); 5. Leaf of Zamites arcticus, Greenland;
6. Cone of Williamsonia gigas (Liassic); 7. Voltzia heterophylla ; 8. Araucaria micro-
phylla (Jurassic). Various reductions. After Wieland, Saporta, Nathorst, Heer, and
Schimper.
apparent that we must look beyond Canada for typical
examples.
JURASSIC PLANTS
Jurassic time is essentially the age of the gymnosperms; it
shows an accentuation of the conditions of the Triassic period,
i.e. the ascendancy of the gymnosperms over the cryptogams
is more pronounced. Cycads occupy the first position and are
represented by a great many genera, of which Nilssonia,
294
ELEMENTARY GEOLOGY
Otozamites, and Williamsonia will serve as examples. The
second place is taken by the conifers like Araucarites and
Pinus, and there is still a con-
siderable survival of horsetails
and ferns. The peculiar maiden-
hair tree (Ginkoales), which pos-
sibly appeared as low as the
Carboniferous, is represented by
a considerable number of species.
JURASSIC INVERTEBRATES
The small unicellular animals
(Protozoa) which first became
important in the Carboniferous
and afterwards somewhat de-
clined are present in great num-
bers in the Jurassic rocks.
Hitherto the importance of
sponges has been slight, as only
in certain formations of the
Silurian and Devonian has it
TWO Australian species. After Muii, from been f ound necessary to refer
Wieland," American Fossil Cycads." iQ them jn the Jurassic> h()W_
ever, sponges are so abundant that they must be mentioned
in the most elementary account of the life.
The skeleton of a sponge is composed of spicules of lime,
silica, or horny matter. Most of the Jurassic sponges were of
the siliceous type, and of these two kinds are known — one in
which the spicules are heavy and strongly interlocked,
lithistid or stony sponges (Cnemidiastrum), and another kind
in which the spicules are delicate six-rayed structures so
arranged as to build up a lattice-like skeleton of extraordinary
delicacy (Craticularia) .
CORALS abounded in favourable localities; they are even
more numerous than in the Triassic and belong to the same
type, the Hexacoralla, which is building up the coral reefs
of to-day.
ECHINODERMS are represented chiefly by sea lilies and sea
urchins. The former are of the soft-crowned, more modern
type, which has been briefly described in the account of
FIG. 150. MODERN CYCADS
THE JURASSIC PERIOD
295
Triassic life. In certain layers of Jurassic rocks crinoids are
found in a wonderful profusion, which is excelled only by the
maximum occurrences of the Carbon-
iferous. The pear encrinite, Apio-
crinus rotundus, and different species
of the genus Extmcrinus are particu-
larly characteristic. The latter genus
is very typical of Post-palaeozoic
crinoids, as it possesses a very long
stem, a small cup with soft crown,
and an extraordinary profusion of
branching arms.
ECHINIDS, or sea urchins, are all
of the modern type, i.e. they have
twenty rows of plates : in this respect
they agree with the Triassic forms.
The prevailing Triassic sea urchin,
with sub-spherical body and with the FIG. 151. LIASSIC CRINOID
mOUth and anal Orifice Situated at Extracrinus sp. From a specimen
,. in the Royal Ontario Museum,
the tWO poles Of the Shell, begins tO Toronto. About one - twelfth
, . , . T , . . j . natural size.
give place to the irregular echimd, in
which the shell becomes depressed, heart-shaped, etc., and
one .or both of the openings are removed to a position near
the margin of the shell. Clypeus and Collyrites are typical
Jurassic genera.
PELECYPODS abound. The archaic types of the Palaeozoic
seas have passed away and their place is taken by the new
life which first made its appearance in the Carboniferous.
The great advance shown in the Triassic is maintained;
numerous new families appear; and genera which persist to
the present day are inaugurated. Trigonia is, perhaps, the
most characteristic of Jurassic pelecypods: Gryphcza, Lima,
and Pecten are also very abundant. Among the genera found
in the Canadian Jurassic rocks are Gryphcea, Pecten, Avicula,
Cardium, and Ostrea.
GASTROPODS are numerous, but they are scarcely as
important as the pelecypods. The class is not so progressive,
as some of the old Palaeozoic genera still survive. The newer
type is predominant, however, and is represented by many
forms in which the mouth of the shell is no longer simple and
FIG. 152. JURASSIC PELECYPODS
Lima gigantea, two-fifths natural size; 2. Gryphcza arcuata, two-fifths natural size.
FIG. 153. SLAB FROM THE JURASSIC OF ENGLAND
?howing many specimens of the pelecypod, Trigon\a clavel\a^a. One-third siz,§,
THE JURASSIC PERIOD
297
rounded as in most Palaeozoic gastropods, but is drawn out
into tube-like extensions. This change in the shell indicates
that the animals had acquired a more specialised way of
taking water into the gill cavity. Nerinea and Purpuriwa
are common forms.
CEPHALOPODS are the most characteristic invertebrate
FIG. 154. LIASSIC AND JURASSIC AMMONITES
i. Amaltheus margaritatus ; 2. Perispkinctes polyplocus ; 3. JF.goceras capricornis • 4. Oxy-
noticeras oxynotus ; 5. Caloceras subarmatus ; 6. Harpoceras bifrons. Figures reduced
from Zittel.
creatures of Jurassic time: they are represented by two
groups, the ammonites and the belemnites.
The order Ammonoidea includes all the cephalopods in
which the suture is angulated, from the primitive clymenoids
to the ammonitoids. Strictly speaking, the term "ammonite "
is • synonymous with "ammonitoid," but it is sometimes
applied to all members of the order. The dominant Jurassic
ammonites were derived from a parent stock which dates
back to the Devonian. This stock was only one of those
298
ELEMENTARY GEOLOGY
which flourished in the Triassic, and it is much modified with
the advent of the Jurassic. This modification seems to consist
in a slight loss of complexity in the
suture, the assumption of a high
degree of external ornamentation,
and the development of an extra-
ordinary number of species.
American Jurassic ammonites are
insignificant in number when com-
pared with the vast fauna of Europe.
Phylloceras, Haploceras, and Peri-
sphinctes are among the commonest
genera.
BELEMNITES are related to the
nautiloids and ammonites, but they
form a shell of a very different char-
acter. Instead of being an external
investment in which the animal lives,
it consists of an elongated structure
enclosed within the body to give
rigidity to the creature. It is thought
that belemnites developed from
Orthoceras by the gradual surround-
ing of the shell by the animal. In
this way the chambered cone of
Orthoceras gradually became con-
verted from an external to an
internal structure. This change rendered useless the empty
chambers of the original shell, which dwindled in consequence ;
at the same time greater strength was given to the structure
by the formation of a thick layer of calcite on the outside. The
final result was a solid cigar-shaped rod of calcite with a small
conical cavity at the anterior end in which the dwarfed
remnants of the original chambered cone remained. Belem-
nites existed in enormous numbers, as their skeletons (cigar
fossils) are crowded in many layers of Jurassic rock. Belem-
nites densus is probably the best known American example.
Numerous belemnites are found in the Jurassic rocks of
British Columbia.
The ARTHROPODS, or invertebrates with jointed limbs, are
FIG. 155. LIASSIC AND
JURASSIC BELEMNITES
Liassic of Dorsetshire;
3. Belemnites canaltculatus,
Lower Oolite of Wiirtemberg.
Reduced from Zittel.
THE JURASSIC PERIOD
299
represented by numerous types, among which the ten-footed
crustaceans, or decapods, and
the dragon-flies are the most
important. The decapods with
long tails, of which the lobster
is an example, are numerous
in the fine-grained lithogra-
phic limestones of Bavaria, e.g.
The Same formation
FIG. 155. JURASSIC DECAPOD
one-sixth natural size. After Zittel.
has yielded many dragon-flies, of which Petalia will serve
as an example.
JURASSIC VERTEBRATES
FISH. The heterocercal ganoids of the Triassic are replaced
in the Jurassic period by a related group, in which this archaic
FIG. 157. SHINING-SCALED GANOIDS OF THE JURASSIC
i. Lepidotus notopterus, one-sixth natural size; 2. Head of Aspidorhynchus acutirostrls.
After Zittel.
form of tail is less pronounced, and in which the scales are
generally thick and covered with a shining enamel. This type
of fish by a thinning of the scales and the acquisition of a
300 ELEMENTARY GEOLOGY
bony skeleton gives rise to the modern bony fish. Between
the shining-scaled ganoid and the bony fish there is no very
sharp line of division. The great importance of these fish
in the Jurassic justifies the citation of several examples
as follows :
Dapedius. Thick scales and deep body.
Lepidotus. Thick scales and fusiform body. Large.
Aspidorhynchus. Thick rhomboidal scales and long, thin
body.
Pachycormus. Thin overlapping scales and long body.
Leptolepis. Thin scales and partly bony skeleton. Shows
the transition to the modern bony fish.
In addition to these ganoids there are many sharks, skates,
rays, and chimeras.
REPTILES. Not only to the scientific worker, but to all
persons of liberal education, the extraordinary reptilian life of
the Mesozoic has appealed in the strongest terms. The
grotesque shape, the varied habitat, and the gigantic pro-
portions of these animals have all contributed to make them
objects of interest and astonishment. Their influence is felt
beyond the realm of pure science : it extends into the field of
popular literature and has even invaded the realm of fiction.
Reptiles dominated the time; they swam in the seas, lorded
over the creatures of the land, infested the marshes, and even
flew in the air.
Palaeontologists believe that water-going reptiles did not
arise directly from fish, but that they descended from land
reptiles which, in search of food or to escape their enemies,
gradually became accustomed to life in the water. This
adaptation was manifested in the Permian, and became more
pronounced in the Triassic. In the Jurassic seas water reptiles
reached a high degree of development, and are represented by
a number of diverse forms.
Ichthyosaurs (fish lizards) were the most abundant type.
These creatures had a long, fish-like body, powerful tail, short
neck, and four limbs in the form of paddles. In some cases
they reached a length of ten metres. Many species are known
from the Jurassic rocks of Europe, and to a less extent from
America, Australia, and New Zealand.
THE JURASSIC PERIOD 301
Plesiosaurs resemble ichthyosaurs, but they are thought to
have descended from a different stock. They rival the ich-
thyosaurs in size and are characterised by a long neck and a
short tail. As the tail is not adapted for a swimming organ
propulsion is effected by the paddles, which are relatively
longer than in the ichthyosaurs. Nothosaurus of the Triassic
was a forerunner of the plesiosaurs, which were numerous in
the Jurassic and continue into the Cretaceous.
Crocodiles are represented by a number of primitive forms
with long thin snouts (teleosaurs), and towards the close of the
period by smaller forms with broad snouts. Sea turtles are
known before the close of the Jurassic, but they attain a
greater prominence in later ages.
Many forms of land reptiles are known, but the greatest
interest is attached to the group named Dinosauria or dino-
saurs. These creatures varied in size from that of a cat to
proportions truly gigantic. They all had short, stout bodies,
long tails, and legs which were very long for reptiles. Instead
of crawling, as most reptiles do, they ran or walked, sometimes
on all- fours and sometimes on the hind limbs only. Anatomists
recognise many distinctive features in dinosaurs, but probably
the most characteristic is this method of progression.
Many dinosaurs have been recorded as occurring in the
Jurassic rocks of North America, but the strata containing
them (Morrison formation) are now believed to be of Cretaceous
age. No dinosaurian remains in rocks of certain Jurassic age
are known in North America.
Dinosaurs are extremely varied and have been classified
in different ways by different authors; in general, it may be
said that there are three types — carnivorous, amphibious,
and beaked.
Carnivorous dinosaurs have large heads, short necks,
clawed digits, long powerful hind limbs and much shorter
fore limbs, and sharp-pointed serrated teeth. This type of
dinosaur is much more important in the Cretaceous, but
complete skeletons of small forms and numerous fragmentary
remains have been found in the Jurassic rocks of Europe.
Amphibious dinosaurs, in all probability, were numerous
in North America during the Jurassic, but owing to the
unfavourable conditions of preservation their remains have
302
ELEMENTARY GEOLOGY
not been found. Their abrupt appearance at the very base
of the Cretaceous leads to the above inference, but in view
of the actual evidence we must regard them as essentially
Lower Cretaceous fossils.
Beaked dinosaurs, despite their great size, are very bird-
like in many points of their anatomy, particularly in the
presence of a horny sheath in the front of the jaws. This is a
large group of dinosaurs of diverse shape and varied habit.
Although of smaller size than the giant amphibious forms,
they reach huge proportions and are remarkable in some cases
FIG. 158. MESOZOIC FLYING REPTILES
i. Rhamphorhynchus, Jurassic, one-seventh size; 2. Scaphognathus crassirostris, Jurassic.
Reduced.
for the peculiar shape of the body and in others for the
extraordinary defensive armour. Scelidosaurus is an un-
armoured form and Omosaurus an armoured type from the
Jurassic of Europe.
Flying reptiles are remarkable creatures which appeared
at the beginning of the Jurassic and continued into the
Cretaceous period with very little essential change. Large and
small forms are known, but all are distinguished by a great
extension of the little finger, which served as a support for a
flap of skin stretched between the fore limb and the side of
the body. This wing-like structure served as an organ of
flight, but it is not to be compared with the true wing of the
THE JURASSIC PERIOD
303
bird. These animals are true reptiles, but their bones are
modified to secure lightness and thus assist the power of
flight. Dimorphodon and Rhamphorhynchus are long-tailed
forms of considerable size; Pterodactylus is a smaller form
with a very short tail.
BIRDS. The earliest bird is known by two well-preserved
skeletons from the lithographic limestone of Bavaria and by
less perfect forms from the Jurassic strata of Wyoming. The
European bird, Arch&opteryx, is about the size of a crow and
FIG. 159. ARCH^EOPTERYX MACRURA, THE FIRST BIRD (JURASSIC)
differs from all modern birds in several particulars, all of
which prove its descent from reptilian ancestors. Both the
upper and the lower jaws are armed with numerous teeth,
the tail is an elongated structure composed of many vertebrae,
and the wing or modified fore limb carries three clawed digits.
MAMMALS. The Mammalia, the highest form of animal life,
differ from the reptiles in numerous ways; they all possess
warm blood, provide milk for the young, are more or less
hairy, and have a more perfect circulatory system. Mammals
are of much higher intelligence than reptiles, and their actions
are controlled by an ability to lay plans, to track their prey,
and to attack their enemies in the most vulnerable parts.
304 ELEMENTARY GEOLOGY
Reptiles exhibit none of these attributes, as their actions seem
to consist of instinctive rushes only.
The most lowly of existing mammals are small egg-laying
forms now living in Australia. These creatures, when young,
have peculiar teeth which are shed in the adult. Teeth of a
very similar character have been found in Triassic rocks, but
whether these are really mammalian is open to question. In
the Jurassic, however, both jaws and teeth are known, which
leave little doubt that diminutive and very primitive mammals
had made their appearance.
The living marsupials (kangaroos, opossums, etc.) are
animals of higher organisation than those referred to in the
last paragraph. Teeth and jaws of small creatures believed
to be marsupials have been found in both Triassic and Jurassic
rocks. The Triassic forms are reptile-like, but the Jurassic
examples are more distinctly mammalian.
CHAPTER XIV
THE CRETACEOUS PERIOD
THIS great system receives its name from the fact that chalk
(creta) is an important constituent of the strata where first
studied in England and France. The inappropriateness of
names founded on rock characteristics is again illustrated by
the word "Cretaceous," for chalk beds are by no means
constant members of the system. The Cretaceous rocks of
Canada, for instance, are practically devoid of chalk, and
even limestone is of rare occurrence.
The Cretaceous system is very complex, and the deposits
of one locality are with difficulty compared with those of
others. Geographical conditions varied greatly, not only in
the different continents, but in different parts of the same
continent. In Europe, for instance, two distinct areas of
deposition are generally recognised, and some authors would
increase the number to three. The strata are different in these
basins, and the faunas, while showing a general parallelism,
have distinctive characters in each area.
In England the earlier Cretaceous deposits in the southern
shires are largely of freshwater origin, while in the north they
are distinctly marine. Wider-spread marine conditions pre-
vailed in the latter part of the period, but no very distinct
division into Upper and Lower Cretaceous was suggested by
the earlier studies of the English strata. On the Continent,
however, such a division is much more apparent, and English
geologists now recognise a formation of dark blue clay
(Gault) as the base of the upper division. The Lower Creta-
ceous formations of Europe indicate mixed marine and
continental conditions of sedimentation, while the Upper
Cretaceous formations are distinctly marine and point to a
very extensive flooding of the continent.
In North America, the break between the Lower and Upper
Cretaceous is still more profound ; indeed, it is so marked that
American geologists separate the strata into two distinct
u 305
306 ELEMENTARY GEOLOGY
systems — Comanchian and Cretaceous — believing that the
break is comparable in magnitude with those that separate
the other great systems. While this subdivision is doubtless
better in accord with the facts as revealed in North America,
it seems inappropriate, nevertheless, to introduce a new
systemic name for strata that are admittedly to be correlated
with the Lower Cretaceous rocks of Europe. In this work we
shall regard the lower series as "Lower Cretaceous," but in
deference to the opinion of many eminent American geologists,
the term "Comanchian" will also be employed.
This general discussion of the Cretaceous period cannot be
concluded without reference to the English chalk. The "White
Cliffs of Albion," famous in history and song, are composed of
chalk of Upper Cretaceous age. This formation is the most
conspicuous member of the Mesozoic strata of Europe, and is
referred o as The Chalk. Nearly the whole of the Upper
Cretaceous rocks of England belong to this series, which is
divided into three subdivisions — the Lower, Middle, and Upper
Chalk. The stone is composed of enormous numbers of the
minute calcareous shells of Protozoa (foraminifers) mingled
with fragments of the shells of other organisms. Nodules
of flint are common, more particularly in the Upper Chalk.
Such a formation could have been made only under typical
marine conditions in a sea into which no sediments were
being discharged.
PHYSICAL EVENTS OF THE CRETACEOUS IN
NORTH AMERICA
We have seen that the whole of eastern North America
remained land throughout the Jurassic period, and we may
conclude that it suffered a large amount of dissection and
erosion. The products of this erosion were carried out to sea
and are still beneath the waters of the Atlantic. Even in
Lower Cretaceous time the sea did not invade the present
land area, but changes in the coast-line made possible the
accumulation of continental deposits along the coastal region.
Lower Cretaceous continental deposits are found more par-
ticularly in Maryland, Virginia, and Georgia.
THE CRETACEOUS PERIOD 307
At the same time continental deposits were formed in
limited areas in the western states, more particularly in
Colorado and Wyoming. These beds (Morrison formation)
are of particular interest as they have revealed some of the
most remarkable dinosaurs yet discovered.
Depression of the continent in Lower Cretaceous time,
which permitted the advance of the sea and the deposition
of marine deposits, occurred over a wide area in the south-
western states, Mexico, and Central America. This series of
deposits is the Comanchian proper. Marine invasions also
occurred on the Pacific border, in British Columbia, Oregon,
Washington, and California.
Owing to the great importance and significance of the
deposits of the Gulf region and Mexico, the local name,
Comanchian, has been elevated to the dignity of a time- term
of systemic rank, and is applied by American geologists to
all Lower Cretaceous formations.
Throughout the world, the Upper Cretaceous is marked by
one of the most extensive floodings of the continental areas
known in geological history. In North America, the eastern
border of the United States, the region surrounding the Gulf
of Mexico, and a wide strip of the Pacific coastal region were
submerged. In addition, and of still greater importance, was
a depression of the interior continental region whereby the
sea covered a wide belt of west-central North America from
the Arctic ocean to the Gulf of Mexico.
In the extreme west of the continent, terrestrial disturbances
were marked throughout the Cretaceous. The most important
movement in the Lower Cretaceous was the elevation of a
long strip of country extending from Alaska to Central
America. The axis of elevation lay some distance east of
the coast and passed through the central region of British
Columbia. The elevation of this strip probably occasioned a
downwarping on either side, and prepared the way for the
advance of the Upper Cretaceous sea into the interior of
the continent and over the region immediately bordering
the Pacific.
Upper Cretaceous time continued to be a period of uplift
and of volcanic activity in the Cordilleran region. Towards
the close of the period the uplifting forces reached a climax
308 ELEMENTARY GEOLOGY
of intensity deserving the name revolution, which is applied
only to terrestrial disturbances on the grandest scale.
In order to better understand the results of this revolution,
it is advisable to review the history of the area affected. We
have seen that in the early Cambrian a trough was formed to
the east of the old Pre-cambrian lands which constituted the
Pacific border of the continent. In this trough sedimentation
FIG. l6o. SKETCH MAP OF NORTH AMERICA IN CRETACEOUS TIME
continued through nearly all the Palaeozoic era. The sea
partially withdrew in the Triassic, but returned in the Jurassic
and Lower Cretaceous periods, adding to the great thickness
of strata already formed in the Rocky Mountain geosyncline.
The mid-continental sea of the Upper Cretaceous overlapped
this region and still further increased the thickness of the
sediments, which are not less than 50,000 feet and probably
much more in total thickness.
It was this region, so long an area of sedimentation, that
THE CRETACEOUS PERIOD 309
was chiefly affected by the revolution at the close of the
Cretaceous. A great thrust acting from the direction of the
Pacific ocean threw the region into immense folds with a
general north-west and south-east trend. These folded masses
of rock were elevated to great heights, crumpled and broken ;
great faults developed in places; and immense masses were
pushed, in some cases for miles, out of their original position.
This great event is known as the Laramide revolution; it
marks the birth of the Rocky mountains and the close of
Mesozoic time.
In other parts of the world mountain-making forces were
at work at the same time. The Appalachians of eastern North
America were re-elevated, the Andes of South America were
formed, and general elevation and mountain-building occurred
in the Old World.
THE CRETACEOUS SYSTEM IN CANADA
In eastern Canada no Cretaceous strata, either continental
or marine, are known. The Upper Cretaceous transgression
which affected the eastern border region of the United States
did not advance as far north as Canada.
In western Canada rocks of this age are of great importance:
their description can be best given under the following four
areas of distribution:
i. THE GREAT PLAINS AREA. The region occupied by the
Cretaceous rocks in the prairie region of western Canada may
be roughly defined as a great triangle, stretching along the
international boundary for 750 miles from the centre of
Manitoba to the foothills of the Rocky mountains and reach-
ing an apex 1000 miles to the north-west in the south-east
corner of Yukon territory. While Cretaceous strata were
undoubtedly formed over the whole of this area, they do not
form the surface rock throughout, as they have been covered
by later formations to a limited extent. The chief of these
areas of later rocks are in southern Saskatchewan and in
western Alberta.
The greater part of the region is covered with a thick
accumulation of glacial and post-glacial deposits which hides
310 ELEMENTARY GEOLOGY
the rocks except where deep river valleys have been cut
through the soils or where the flanks of minor elevations
have been eroded.
The rocks of this area were formed in the great shallow sea
of Upper Cretaceous age which covered the heart of the
continent. This sea was doubtless subject to many minor
fluctuations which resulted in local deposits, and in its later
stages, particularly in the western part, it passed into the
condition of brackish and even freshwater lakes. Owing to
the above facts and the scattered nature of the accessible
exposures, it has not yet been possible to accurately correlate
all the formations of this great region.
The Upper Cretaceous rocks of this area may be arranged
in three divisions, erroneously but usually called "groups,"
above which lies a fourth division of less magnitude, as
follows :
Edmonton formation.
Montana group.
Colorado group.
Dakota group.
The Dakota group in Canada is composed essentially of
sandstone which is largely of freshwater origin. Exposures
of the rock are of rather rare occurrence: the most typical
are to be seen in the valleys of the rivers entering Lake
Winnipegosis from the west. The stone is soft, incoherent,
and of no particular value.
The Dakota, if it occurs, is so deeply buried under the later
rocks all the way across the prairies that it is not seen again
until brought to the surface by the folding which produced
the foothills of the Rocky mountains. Exposures may be
seen in the coal-mining districts of the foothills and in the
lengthwise valley west of the first great range of mountains.
At the Sweetgrass hills in Montana, just south of the inter-
national boundary, the Dakota group is much better exposed
than at any point in Alberta. The section shows more than
500 feet of shale, sandy shale, and sandstone. The stone of the
mountains differs greatly from that of Manitoba, as it is very
hard and of green or bluish-green colour. At so great a
distance from the Manitoba outcrops it is questionable
THE CRETACEOUS PERIOD 311
whether this formation is to be strictly correlated with the
eastern sandstone.
The Colorado group is divisible into two formations — a
lower (Benton) and an upper (Niobrara). Exposures occur in
Manitoba and in the foothills, but across the Great Plains the
formations are covered by the rocks of the Montana group.
As revealed by bore-holes in southern Alberta the group is
nearly 2000 feet thick, but the average is probably much less.
FIG. l6l. SKETCH MAP SHOWING THE CRETACEOUS AND TERTIARY ROCKS
OF THE GREAT PLAINS
Cretaceous, black; Mixed Cretaceous and Tertiary, dotted; Tertiary, the white areas
within the black. The Cretaceous and Tertiary of British Columbia not shown.
The Benton formation consists essentially of shale and there
is much soft clay carrying a large amount of colloidal silica.
This material (bentonite) has a remarkable property of re-
taining water, which makes it a very valuable constituent of
the soils derived from the decay of the Benton shales and
other formations.
The Niobrara formation also is largely composed of clay
or shale, but it is much more calcareous than the Benton shale
and even contains thin layers of limestone in places. The form-
ation is recognised with certainty only in the eastern exposures.
312 ELEMENTARY GEOLOGY
The areal extent of the Dakota and Colorado groups is
insignificant when compared with that of the Montana group,
which forms the surface rock over nearly the whole of the
Cretaceous region of the Great Plains. There are two facies
of Montana deposits : marine, and brackish to freshwater. In
the eastern part of the region, the marine facies, Pierre forma-
tion, is alone developed, but in the west the brackish water
deposits, Belly River formation, occur between an upper and
a lower series of marine strata. The Pierre formation is mostly
shale, and much of it presents the same colloidal properties as
the Benton shale. The Belly River beds are composed of soft
sandstones and shales.
The Edmonton formation is very similar to the Belly River
in the character of its rocks, consisting of soft, incoherent
sandstones, sandy shales, and shales. The formation overlies
the upper marine beds of the Pierre over a considerable area
in central Alberta.
The conditions of shallow and brackish water under which
the Belly River and Edmonton beds were deposited favoured
the formation of layers of coal. Owing to the relatively short
lapse of time and the lack of severe terrestrial disturbances
since the beds were formed, coal-forming has not proceeded
beyond the earlier stages; in consequence, nearly all the
coal is lignitic or sub-bituminous. At Lethbridge, however,
the coal is of bituminous grade.
In the Belly River formation Bowling estimates that 33,192
square miles are underlaid by coal beds which contain a
reserve of 223,358,000,000 metric tons. The principal mines
are situated in the vicinity of Lethbridge, Alberta. The same
authority estimates a maximum reserve of 800,958,000,000
metric tons and a more certain reserve of 383,697,000,000
metric tons in the Edmonton formation. The chief collieries
are near Drumheller on the Red Deer river, near Edmonton,
and in the foothills.
The importance of the colloidal clays has already been
referred to. The water-holding clay soils (gumbo) owe their
valuable property of retaining moisture to the hydrated silica
derived from the decay of Benton and Pierre shales.
These colloidal clays are not suitable for brick-making,
but some of the upper non-colloidal clays of the Pierre
THE CRETACEOUS PERIOD 313
(Odanah) as well as the brackish water clays are used for
this purpose.
Natural gas is another important product from the Creta-
ceous formations, more particularly of Alberta. The gas
reservoirs are in the Dakota sandstone; they are tapped by
deep holes through the overlying strata, more particularly
at Medicine Hat and Bow island. Far to the north, on the
Athabasca river, are the so-called tar-sands — sandstones of
Dakota age highly impregnated with bitumen : they are thought
to represent a future source of important industrial products.
2. THE ROCKY MOUNTAIN AREA. We have seen that the
Rocky Mountain geosyncline was an area of sedimentation in
the Lower Cretaceous. The strata consist of an upper and a
lower sandstone with coal-bearing measures between. The
presence of beds of coal and fossil plants indicates that this
series, the Kootenay, is of freshwater origin. The greatest
thickness, nearly 4000 feet, is along the main axis of the
Rocky mountains; eastward, the strata thin out rapidly and
are overlapped by Upper Cretaceous rocks. The upraising of
the mountains at the close of the Cretaceous affected all these
rocks, but subsequent erosion has removed them from the
summits of the ranges. Kootenay strata, therefore, are found
to a limited extent in the foothills, but on a larger scale in
the valleys between the more easterly ranges of the mountains.
The coal of the Kootenay formation is a high-grade bitu-
minous, ranging to anthracite in places. Numerous fields
occur in the long narrow valleys between the ranges; the
most important is the Crowsnest field in British Columbia, in
which the reserve is estimated at more than 56,000,000,000
metric tons, with a workable reserve of 23,000,000,000 metric
tons. The centre of this field is Fernie, British Columbia.
The more important coal-mining centres on the Alberta side
of the boundary are at Coleman on the Crowsnest line, and
at Bankhead on the main line of the Canadian Pacific Railway.
3. INTERIOR PLATEAU AREA OF BRITISH COLUMBIA. In
the interior of British Columbia, between the Coast Range and
the Columbia mountains, are many disconnected areas of
coarse sediments of Cretaceous age ; these are generally mixed
with contemporaneous volcanic matter. In northern British
Columbia coal fields occur in these areas. .
314 ELEMENTARY GEOLOGY
4. PACIFIC COAST AND ISLANDS AREA. Fossiliferous sand-
stones, shales, and conglomerates of Upper Cretaceous age
constitute the Queen Charlotte series, which carries workable
beds of coal on the islands and is known to occur elsewhere.
On the north-east side of Vancouver island and on the
adjacent small islands of the Strait of Georgia, Upper
Cretaceous sandstones and shales, the Cowichan group, are
well exposed. Coal mines of considerable importance are
worked in these rocks at Nanaimo, Comox, and other places
in the vicinity. Excellent sandstone for building purposes
is quarried on Gabriola, Saturna, and other islands of the
Strait of Georgia.
LIFE OF THE CRETACEOUS
CRETACEOUS PLANTS
In Lower Cretaceous time the vegetation shows the same
predominance of cycads that characterised the Jurassic
period; in the upper division, however, the angiosperms, or
higher flowering plants, begin to assert the supremacy they
still enjoy. In late Lower Cretaceous time cycads and conifers
began to wane and trees like the sassafras and poplar appeared.
Before the close of the Upper Cretaceous the flora was dis-
tinctly of modern aspect, with species of birch, maple, oak,
walnut, and many other familiar trees. With these plants
were mingled species of magnolia, fig, and cinnamon, indi-
cating a warmer climate.
The brackish water beds of western Canada have furnished
the remains of a long list of plants : probably the most striking
fossils are the large silicified trunks of a species of cypress
which are common in the Edmonton formation of Alberta.
CRETACEOUS INVERTEBRATES
PROTOZOA reach a high degree of development, as the
remains of these minute organisms form a large part of the
Chalk of Europe. The more calcareous parts of the Niobrara
formation of Manitoba contain numerous protozoans.
SPONGES, both siliceous and calcareous, are common in the
THE CRETACEOUS PERIOD
315
Cretaceous of Europe, but in North America they are of less
frequent occurrence. The flints of the English Chalk are
formed by the accretion of dissolved silica derived from the
spicules of siliceous sponges.
CORALS are abundant in the Cretaceous rocks of some
regions, but they are rare in Canada. The conditions under
which the prevailing shales were deposited did not favour the
life of corals.
ECHINODERMS are represented chiefly by sea urchins which
show an advancing tendency to irregular form. The peculiar
stemless Uintacrinus
with remarkably long
arms is a characteristic
fossil of the Cretaceous
of Kansas. Hemiaster
Humphrey 'sianus is the
only sea urchin from the
Upper Cretaceous rocks
of the Great Plains, and
is of rare occurrence.
PELECYPODS are very
numerous, and some
peculiar forms are par-
ticularly characteristic
of Cretaceous time: of
these, Hippurites and FIG' l62' CRETACEOUS CRINOID
•* Uintacnnus sociahs. Much reduced.
related forms, with one
valve extremely small and placed like a cover on the
larger valve, are eminently Cretaceous. The commonest
genera in the marine Cretaceous rocks of western Canada
are Arctica, Inoceramus, Gervillia, Pteria, Ostrea, and
Liopistha. The brackish water beds of the Belly River series
are in places crowded with oysters : Corbula and Corbicula are
also very abundant.
GASTROPODS are numerous and show a normal advance on
the Jurassic type, but they present no especial features for
general comment. Anisomyon, Lunatia, and Anchura are
perhaps the commonest Canadian genera.
CEPHALOPODS are represented by many belemnites and
ammonites. The former require no particular mention, but
FIG. 163. CRETACEOUS PELECYPODS
Arctica ovata alia ; 2. 'Arctica ovata; 3. Ostrea subtrigonalis ; 4. Ostrea glabra ; 5.
Inoceramus barabini ; 6. Pteria linguifera ; 7. Liopistha undata ; 8. Corbula per-
angulata ; 9. Pteria nebrascana ; 10. Corbicula occidentalis ; n. Protocardia borealis ;
12. Volsella meeki ; 13. Modiola attenuata. All figures six-sevenths natural size. After
Whiteaves, Meek and Hayden, and from original photographs.
FIG. 164. CRETACEOUS PELECYPOD
Slab of red Cretaceous sandstone from the Red Deer river, Alberta, with Inoceramus vanuxemi.
One-fourth natural size.
FIG. 165. CRETACEOUS GASTROPODS
i. Campeloma producta ; 2. Melania insculpta ; 3. Anisomyon centrals ; 4. Viviparus leai;
5. Anchura americana ; 6. V anikoropsi<> tuomeyanu ; 8. Lunatia concinna. All figures
about natural size. From Meek and Hayden and from photographs of species from western
Canada.
3i8 ELEMENTARY GEOLOGY
the latter show evidence of decadence. While many typical
ammonites with closely coiled shell still survive, the senile
condition of the race is indicated by the assumption of peculiar
form. Instead of the typical coiled shell, we find straight
(Baculites), hook-shaped (Hamites), open-coiled (Crioceras),
turreted (Turrilites), and many other erratic forms. This
tendency to strange shape seems to be the precursor of
extinction, for no ammonites are known after the Cretaceous.
One of the commonest fossils of our western Cretaceous is
the straight-shelled Baculites, of which several species are
known. The fragments of this fossil are commonly mistaken
for fish. A very large ammonite, Placenticeras whitfieldi, is
also a common fossil in the Cretaceous of the plains. The
Upper Cretaceous strata of Vancouver and Queen Charlotte
islands have yielded a rich and varied ammonite fauna.
ARTHROPODS are well represented and show a great increase
in the broad-shelled decapods or crabs. These fossils are rare
in the Montana group of the plains, but ten species are known
from the Cowichan rocks of Vancouver island.
CRETACEOUS VERTEBRATES
FISH show a pronounced change in Cretaceous time, as the
old type with skeleton of cartilage gradually gives place to
the teleosts with true bony skeleton and thin, flexible, over-
lapping scales. In other words, the modern type of fish gains
an ascendancy over the typical Mesozoic type, and is repre-
sented, before the close of the period, by such familiar fish
as salmon, herring, and other common forms. Some of the
Cretaceous fish were of great size and predaceous habits:
Portheus was twelve to fifteen feet in length and the mouth
was armed with a truly formidable series of teeth. Sharks
were still numerous and were closely related to modern types.
REPTILES. The Cretaceous system equals and probably
exceeds the Jurassic in the number and variety of the
reptilian remains. The inclusion of the famous Morrison
beds of Wyoming and Colorado in the Cretaceous transfers
to this system many of the largest and best known dinosaurs
which were formerly believed to be of Jurassic age.
Ichthyosaurs resembling those of the Jurassic occur, but
THE CRETACEOUS PERIOD 319
less frequently, in the Lower Cretaceous: they do not survive
the middle of the Upper Cretaceous.
FIG. 166. CRETACEOUS ECHINIDS AND CEPHALOPODS
Baculttes ovatus, specimen from Peace river with the outer shell; 2. Baculites sp. with the
outer shell removed showing the sutures; 3. Hemiaster humphreysianus ; 4. Scaphites
subglobosus; 5. Placenticeras whitfieldi. Reduced. After Whiteaves and Meek.
Plesiosaurs are more abundant in Cretaceous than in
Jurassic time : they reach their maximum development in the
later part of the period and survive until its close. Some of
ELEMENTARY GEOLOGY
these creatures were of great size: the head of the largest
form known was about five feet long, and the smallest species
was fully ten feet in length. Elasmosaurus platyurus, the
FIG. 167. UPPER CRETACEOUS PLESIOSAUR
Elasmosaurus platyurus with an ichthyosaur, flying reptiles, and the diving bird Hesperornis.
From Williston, " Water Reptiles, Past and Present."
longest-necked plesiosaur, shows the following proportions:
head, two feet; neck, twenty- three feet; body, nine feet;
tail, seven feet.
FIG. 168. CRETACEOUS MOSASAUR
Thylosaurus dyspelor, one-nineteenth natural size. From " Memoirs of the American
Museum of Natural History."
While the remains of plesiosaurs are not particularly
numerous they have, nevertheless, been recorded from all
parts of the world where marine Cretaceous strata occur.
Cimoliosaurus magnus from the Belly River formation of
Alberta is the only Canadian example.
THE CRETACEOUS PERIOD
321
A new type of aquatic reptile appeared in the Upper
Cretaceous and existed in large numbers in many parts of
the world. Thousands of specimens have been obtained from
the chalk beds of ....
Kansas alone. These
creatures, known
THE GREAT AMPHIBIOUS DINOSAUR
Brontosaurus excelsus.
as mosasaurs, were
very long - bodied,
almost snake-like,
and were provided FIG. 169.
with four " paddles ' '
or modified limbs differing greatly from those of ichthyosaurs
and plesiosaurs. The structure of the skeleton is very peculiar,
and indicates a totally different ancestry from that of the
other aquatic reptiles. They were not unlike the mythical
sea-serpent. In size the known forms range from eight to
forty feet in length. Platecarpus is one of the best known
American genera.
Among the water reptiles, turtles and crocodiles played an
important role. Several very large turtles occur in the Belly
River beds of Alberta, also a few crocodiles.
FIG. lyo. THE GREAT AMPHIBIOUS DINOSAUR
Dipledocus carnegii, eighty-seven feet long.
The dinosaurs, or great land reptiles, were even more
numerous and diversified than in the Jurassic: they may
be conveniently considered as belonging to three general types,
as -follows:
"Amphibious dinosaurs were the Giant Reptiles par excel-
lence, for all of them were of enormous size, and some were
by far the largest of all four-footed animals, exceeded in bulk
only by the modern whales. In contrast to the carnivorous
x
322
ELEMENTARY GEOLOGY
dinosaurs these are quadrupedal, with very small head, blunt
teeth, long giraffe-like neck, elephantine body and limbs, long
FIG. 171. CRETACEOUS CARNIVOROUS DINOSAUR
Gorgosaurus libratus. From Belly River formation of Alberta. About i-ioo natural size.
After Lambe.
massive tail prolonged at the end into a whiplash as in the
lizards. Like the elephant, they had five short toes on each
foot, probably buried in life in a soft pad, but the inner digits
FIG. 172. CRETACEOUS CARNIVOROUS DINOSAUR
Head of Tyrannosaurus rex. About one-twentieth natural size. By permission of the
American Museum of Natural History.
bear large claws, blunt like those of turtles, one in the fore
foot, three in the hind foot." A
1 " Dinosaurs," W. D. Matthew, A merican Museum of Natural History.
THE CRETACEOUS PERIOD
323
Brontosaurus, a form from the Lower Cretaceous of North
America, measuring sixty-six feet eight inches in length, is one
of the best known of these giant reptiles. A skeleton of
Diplodocus in the Carnegie Museum at Pittsburg is eighty-
seven feet in length, but indicates an animal of somewhat more
FIG. 173. CRETACEOUS TRACHODONT DINOSAURS
i. Corythosaurus casuarius, photograph and drawing of the specimen in the American Museum
of ^Natural History, New York. 2. Saurolophus osborni, Edmonton formation, Alberta.
Photograph of specimen in American Museum of Natural History, New York. No. I
about one-sixtieth natural size, No. 2 about one-fifty-eighth natural size. After Brown, by
permission of the A merican Museum of Natural History.
slender proportions than Brontosaurus. Even larger forms are
known to occur in the Cretaceous strata of Kenia in Africa.
The general features of carnivorous dinosaurs have been
briefly described on page 301 : in the Cretaceous period they
reached remarkable dimensions and were doubtless the lords
of creation. The largest known carnivorous dinosaur, well
324
ELEMENTARY GEOLOGY
named Tymnnosaurus rex (tyrant saurian king), was forty-
seven feet long; standing in erect position, it was eighteen
to twenty feet high. The head, four feet three inches long,
FIG. 174. EUROPEAN CRETACEOUS BEAKED DINOSAUR
Iguanodonbernissartensis. About i-uoth natural size. After Marsh.
was armed with a formidable array of sharp pointed teeth
from three to six inches in length. A related form, Gorgo-
saurus, from the Belly River beds of Alberta, is twenty-nine
feet long and. shows
the characteristic
diminution of the
fore limbs to an ex-
treme degree.
The beaked dino-
saurs probably in-
clude the most
remarkable animals
in all history ; known
first from the Juras-
sic, they reach a
FIG. 175. CRETACEOUS HORNED DINOSAURS
Heads of different genera. Greatly reduced. From Matthew
" Dinosaurs," American Museum of Natural History.
wonderful develop-
ment in the Creta-
ceous. Of the
unarmoured kinds, Iguanodon from Belgium and the tracho-
donts of North America are known by many complete skeletons.
Trachodont dinosaurs are so named on account of the peculiar
THE CRETACEOUS PERIOD
325
teeth, which are numerous and set closely together to form a
sort of inclined mashing surface. They are also known as
"duck-billed dinosaurs" in reference to the shape of the
predentary bones, which resemble the bill of a duck. In
erect position these animals reached a height of about sixteen
feet: they are characteristic of Upper Cretaceous time, and
continued until its close.
Both the Edmonton and Belly River beds of Alberta,
where exposed in the valley of the Red Deer river, have
'A
FIG. 176. CRETACEOUS HORNED DINOSAURS
Monoclonius amid typical Belly River vegetation. From Deckert and Brown,
Museum of Natural History."
'American
yielded many skeletons of these dinosaurs. Fragmentary
bones may be collected in places literally by the wagon load.
Saurolophus, with a spine at the back of the head, is of frequent
occurrence in the Edmonton beds, and Corythosaurus, with a
plate-like crest on the skull, is a typical Belly River example.
Jhe development of armour in the beaked, vegetable-
feeding dinosaurs is the natural outcome of the attacks of the
giant carnivorous forms. Many and varied are the methods
of defence and extraordinary the results, as these creatures
are among the most grotesque animals known. Stegosaurus,
a Lower Cretaceous form contemporary with Brontosaurus,
a
« i
§1
o §
3«
o£
I
THE CRETACEOUS PERIOD 327
was armed by a double row of great plates along the back:
the largest of these plates was more than two feet in length.
The Ceratopsia include a number of extraordinary animals in
which the skull was armed with horns and extended back-
wards into a great fringe around the neck. The Belly River
formation of Alberta has yielded a number of forms, Ceratops,
Styracosaurus, Centrosaurus, and Monoclonius, in which the
fringe is pierced by openings or drawn out into finger-like
extensions. The Edmonton formation yields a similar form,
Anchiceratops ; and the best known animal of all, Triceratops,
with a solid fringe and three horns, occurs in the uppermost
Cretaceous beds of Wyoming.
A different type of armour is seen in Ankylosaurus, a huge,
flat-bodied creature covered from the snout to the end of the
tail with great bony plates set closely together: it has been
described as "the most ponderous animated citadel that the
world has ever seen." This wonderful animal was made
known to science chiefly by discoveries in the Edmonton
formation of Alberta.
BIRDS. Two peculiar birds have been found in the Cretaceous
of North America: one, Hesperornis, was a large wingless
diving bird, reptile-like, with teeth except in the front of the
upper jaw; the other, Ichthyornis, was smaller, with similar
dentition, but with large wings and a carinate breast.
MAMMALS. Small archaic mammals resembling those of the
Jurassic are known from Cretaceous rocks, but the ascendancy
of this type of life is yet to come.
During Cretaceous time the conditions of our prairie region
must have been as different as possible from those now pre-
vailing. Instead of the bare plains with severe winters there
were great forests like those of Pennsylvania or Alabama,
suggesting a warm climate ; and the inhabitants of the region,
the grotesque and sometimes gigantic reptiles, dragging their
length among the marsh grasses of the lagoons or springing,
kangaroo-like, through the drier openings in the forest must
have been even more different from anything Canadian of the
present day. It was the triumphant time of the cold-blooded,
egg-laying animals, when bulk and brute force ruled the
world instead of brains.
CHAPTER XV
SUMMARY OF THE MESOZOIC ERA
HAVING reviewed the march of events and the evolution of
life through the periods of the Mesozoic, we are now in a
position to form a conception of the era as a whole.
The Mesozoic was ushered in by one revolution, the Appal-
achian, and brought to a close by another, the Laramide.
Throughout the era there was much terrestrial disturb-
ance, mountain-building, and volcanic activity. The strata
formed during the time are very diversified, of different
facies, and usually local in development.
In North America
nearly the whole of Meso-
zoic history was written
in the western half of the
continent ; in Canada this
is even more striking, for,
with the exception of a
small area of Triassic
rocks in Nova Scotia,
there are no strata of
this age east of Manitoba.
Coal was formed in
large amounts in Mesozoic
time ; nearly all the coal
of western Canada is
derived from Cretaceous rocks, and it is obtained from the
Cretaceous and other systems of the Mesozoic in different
parts of the world.
The Mesozoic, as the name implies, was the time of " middle
life" — the time between the archaic Palaeozoic and the type
of life now existing. Although the Mesozoic life evolved from
that of the Palaeozoic and is not separated from it by a break
of the nature of a catastrophe, there is, nevertheless, a very
great difference in the life of the two eras. Brachiopods ruled
328
FIG. 178. CRETACEOUS TURTLE
A spider etes foveatus from the Cretaceous of Alberta.
About one-sixth size. From Hay, " Fossil Turtles
of North America."
SUMMARY OF MESOZOIC ERA 329
among the shell fish of the Palaeozoic, molluscs took their
place in the Mesozoic; nautiloid cephalopods characterise
the Palaeozoic, ammonites succeeded them in the Mesozoic;
cystids and blastoids and stony- vaulted sea lilies predominate
in the Palaeozoic, in the Mesozoic the two former groups dis-
appear and the last is replaced by a type of crinoid with soft
crown; the vascular cryptogams give place to the gymno-
sperms, and the armour-plated fish yield to the ganoids.
FIG. 179. CRETACEOUS WADING BIRD
Hesperorms regalis. One-twentieth natural size. After Marsh,
Above all else, however, the Mesozoic is unique in the
number, diverse form, and great size of its reptiles: it is the
Age of Reptiles.
Negatively the Mesozoic may be distinguished from the
Palaeozoic by the absence of trilobites, graptolites, blastoids,
cystids, stromatoporoids, and armour-plated fish; positively
it is marked by the presence of reptiles, ammonites, belemnites,
and cycads.
Towards the end of the Mesozoic many organic changes
took place, and the forerunners of the great life of the next
era began to appear.
CHAPTER XVI
THE CENOZOIC ERA— THE TERTIARY PERIOD
THE Cenozoic era, or time of Recent Life, covers the history of
the world from the close of the Mesozoic to the present. The
early geologists applied the name Tertiary to all the rocks
formed between the close of the Mesozoic and the opening of
Recent time, as they were believed to represent the third great
system. Later the term Quaternary was introduced to include
the Recent and the time immediately preceding it. Authors
are not yet agreed as to the exact way in which these old
terms should be used in the light of modern knowledge. The
classification adopted for this book is indicated in the table
on page 331.
We have seen that a profound disturbance, the Laramide
revolution, marked the close of the Mesozoic and resulted
in great elevations of the lands in many parts of the world.
Before the seas of the new era could advance, the rejuvenated
continents must have been reduced by erosion or depressed
by terrestrial movements. Time is required for these changes
to be brought about, and an unrecorded interval is indicated
by the fact that the Tertiary strata nearly everywhere rest
with marked unconformity on the underlying rocks. This gap,
however, is by no means so profound as was formerly believed,
for rocks have been found showing an intermingling of
Cretaceous and early Tertiary fossils. Also, where marine
evidence fails, the story of the interval is revealed by strata
of freshwater origin.
The Tertiary rocks of England rest unconformably on the
Chalk, which had suffered profound erosion in the interval;
on the other hand, the Tertiary strata of southern Europe
cannot be sharply defined from the underlying Cretaceous.
Freshwater Tertiary strata, in Canada and the United States,
fade imperceptibly through brackish water deposits into the
marine Cretaceous rocks.
330
THE CENOZOIC ERA
331
The prevailing high lands at the opening of the Tertiary
naturally resulted in a separation of the waters; later, when
marine transgressions occurred, Tertiary deposits were made
in isolated basins resulting in great diversity in the character
of the rocks and in their organic remains. This local character
of Tertiary formations is further increased by the important
part played by fresh water in building up the strata.
Tertiary rocks, except where affected by mountain-making
forces, are generally soft and incoherent, approximately
horizontal, and charged with fossils in a relatively fresh and
unaltered condition.
With the Tertiary period began the type of life now existing.
Very early in the period appeared some species of molluscs
which inhabit the present seas, and as time went on more and
more of existing species were evolved. On this basis the
pioneers of Tertiary geology divided the period into three
epochs — Eocene (dawn of recent), Miocene (less recent), and
Pliocene (more recent) . Subsequent investigations have made
it advisable to increase the number of epochs as indicated
in the following table, which is taken from Pirrson and
Schuchert's Textbook of Geology.
CLASSIFICATION OF THE TERTIARY PERIOD
PERIOD
EPOCH
LIFE
Tertiary
Neogene
Pliocene
90 to 100 per cent, of living
molluscs
Miocene
20 to 40 per cent, of living
molluscs
Paleogene
Oligocene
Eocene
10 to . 15 per cent, of living
molluscs
i to 5 per cent, of living molluscs
Paleocene
Practically no living molluscs
'During Tertiary time the present distribution of land and
water was developed; in other words, geography as we know
it to-day was established. During this time great terrestrial
disturbances took place and many of the great mountain
systems of the world received their final uplift, e.g. the
332 ELEMENTARY GEOLOGY
Pyrenees, the Alps, the Rockies, and the Himalayas. Vast
quantities of molten matter were ejected from the interior of
the earth, and masses of lava hundreds of feet in thickness
were distributed over thousands of square miles of territory in
many parts of the world.
While most marine Tertiary rocks are very local in char-
acter, formations of wide distribution were formed in a sea
that extended across southern Europe, Asia Minor, and east-
ward to Burma and the Indian ocean. In Eocene time a
limestone formation filled with vast numbers of the protozoan
Nummulites was formed in this sea. As evidence of the
profound changes of Tertiary time, this Nummulite limestone
is found at an elevation of 10,000 feet above the sea in the
Alps, 11,000 in the Pyrenees, and 19,000 in the Himalayas.
The great terrestrial changes of the Tertiary, or other causes
of which we have no knowledge, seem to have produced
remarkable variations in climate, especially in the northern
hemisphere. Early Eocene time was temperate, but later in
this epoch the climate became tropical into high latitudes and
continued to be at least sub-tropical during the Miocene, as
forests of this age flourished as far north as Spitzbergen.
With the Pliocene the temperature fell in the northern hemi-
sphere, and by its close it had become so cold that ice and
snow covered vast areas extending well into the temperate
zone. This refrigeration was coincident with the stupendous
uplifting of mountain ranges which marked the Pliocene : the
two events, mountain-making and refrigeration, brought the
Tertiary period to a close.
PHYSICAL EVENTS OF THE TERTIARY IN
NORTH AMERICA
The visible record of Tertiary events in North America, as in
other parts of the world, is found only to a limited extent in
strata of marine origin. The period opened with an elevated
continent ; in consequence, most of the marine deposits are still
under the sea. At no time did oceanic waters cover more than
a very small fraction of the present land area, and these
invasions were confined to comparatively narrow strips along
THE CENOZOIC ERA 333
the Atlantic and Pacific oceans and the Gulf of Mexico. In
the interior of the continent, however, freshwater deposits
on an extensive scale have preserved a record of physical
events and of organic evolution. These freshwater deposits
are extensively developed in the Western States and Canada:
some authorities believe them to be of lacustrine or lake
origin, while others regard them as flood-plain accumulations
from rivers. Tertiary history is also recorded in great masses
of volcanic rock, in displaced strata, and in profound erosion.
An interval of comparative quiet followed the Laramide
revolution, and freshwater deposits of Paleocene age were
made in the western continental region in isolated basins
from Mexico to Canada. In early Eocene time the upthrust
of the Laramide revolution was renewed in the Cordilleran
region, and was accompanied by much volcanic activity. A
long period of erosion and local accumulation of strata
followed during the Eocene and early Oligocene. Marine
overlaps occurred during this period of erosion, and Eocene
strata were deposited along the southern Atlantic border in
Maryland, Delaware, and Virginia ; to a greater extent around
the Gulf of Mexico ; and in limited strips in California, Oregon
and Washington, extending into Canada in the vicinity of
Vancouver.
With Middle Miocene time crustal disturbances began
again on a grand scale; pre-existing mountain ranges were
elevated, new mountains formed, and vast quantities of molten
rock ejected. The Pacific region was most seriously affected
by this renewed activity. Volcanoes poured out ashes and
lava along the whole Pacific border from Central America
to Alaska: in the basin of the Columbia river alone, lava
flows covered more than 200,000 square miles to a depth of
at least 4000 feet. It is thought that a land barrier which had
formerly bridged the Atlantic by way of Greenland, Iceland,
and the Faroe islands broke down at this time, permitting
the cold waters of the Arctic to advance down the eastern
American coast. These northern disturbances were accom-
panied by tremendous flows of lava, of which the Giant's
Causeway of Ireland is a remarkable example.
During Oligocene and Miocene time freshwater strata con-
tinued to be formed in the western continental region, and
334 ELEMENTARY GEOLOGY
oceanic overlaps occurred along the Atlantic, Gulf, and Pacific
borders. In the Atlantic and Gulf areas of deposition numerous
local formations of Oligocene and Lower Miocene age rest
unconformably on the Eocene. The profound disturbances of
Middle Miocene time are indicated by the practical absence
of rocks of that age and the strong unconformity between the
strata of the Lower and Upper Miocene.
Miocene marine overlaps occurred in the Pacific border
region : strata of this age in California show the same evidence
of a great disturbance about the middle of the epoch. On
the British Columbia and Alaska coasts there is no certain
evidence of marine deposits until late in Miocene time.
The Pliocene was a period of great elevation in the Cordil-
leran region and of extensive volcanic activity: then appeared
the great series of volcanoes, Ranier, Shasta, Baker and many
others, which continued active into later time. Eastern North
America also was elevated, and the continent assumed the
general geographical outline it still shows.
Marine deposits of the Pliocene are scattered and of little
extent: most of the Pliocene accumulations are still under
the sea.
THE TERTIARY SYSTEM IN CANADA
Evidences of marine transgression in eastern Canada are
doubtful, but the march of events is recorded in extensive
erosion and changes of level. Continental deposits, consisting
of older rock decayed in situ and coarse sands and gravel,
occur sparingly in the maritime provinces.
The withdrawal of the Cretaceous seas from the region of
the Great Plains after the Laramide revolution made land of
the sea floor over the greater part of the area. This with-
drawal, being gradual, resulted in a freshening of the water
that remained in restricted areas towards the close of the
Cretaceous. In consequence, the latest Cretaceous deposits
are of brackish or even freshwater origin. We have seen that
in central Alberta a large area was covered by these residual
waters, in which the brackish-water Edmonton formation
was deposited. In southern Saskatchewan was another such
THE CENOZOIC ERA 335
basin, in which somewhat later Cretaceous strata (Lance?)
were deposited in waters probably fresher than those of the
Edmonton basin.
With the opening of the Paleocene, the waters of both these
basins had become quite fresh and deposits of sands and
shales were made on an extensive scale. In Alberta we have
the Paskapoo formation conformably overlying the Edmon-
ton, and in southern Saskatchewan the Estevan beds (Fort
Union formation of American geologists) similarly related
to the Lance.
The Paskapoo sandstones are quarried in the vicinity of
Calgary and at other points for building purposes. Both
Paskapoo and Estevan shales are used for brick and tile-
making, and numerous workable coal seams occur in the
latter formation in the Estevan, Wood Mountain, and Willow-
bunch districts of southern Saskatchewan. The coal is a soft
lignite: its use has hitherto been restricted by a tendency to
disintegration on storage or transportation, but it is hoped
that its use at a distance will be made possible by a process
of briquetting.
West of the main Tertiary area of southern Saskatchewan,
in the Cypress hills, conglomerates, sandstones, and clays of
Oligocene age unconformably overlie the Paleocene deposits.
In the time of comparative quiescence following the Lara-
mide revolution, continental deposits doubtless accumulated
in the intermontane region of British Columbia, but subse-
quent erosion and volcanic activity have obscured the record
to a great extent. In the vicinity of Kamloops are beds of
sandstone, conglomerate and shale of Eocene age, the Cold-
water group. These beds were upturned and eroded before
the extrusion of the late Tertiary volcanics, thus bearing
evidence to the general deformation of the region in Miocene
time. The Coldwater beds are by no means negligible, as their
thickness has been estimated at 5000 feet : this mass of debris
bears witness to the large amount of erosion accomplished
during the Eocene.
Oligocene time was marked in this region by extensive
extrusions of basalt from fissures. Daly thinks that these
great masses of igneous rock interfered with the drainage
and that basins were formed in which freshwater muds and
336
ELEMENTARY GEOLOGY
sands accumulated during the Oligocene and possibly also
the Miocene (Tranquille group). The igneous rocks (Kamloops
volcanic group of Drysdale) are estimated to have had origin-
ally an average thickness of 3000 feet. Volcanic rocks of
the Oligocene and Miocene occur extensively throughout the
interior region of British Columbia, and are largely responsible
for the introduction of the gold, silver, and copper ores of the
mining regions of the southern part of the province. Coals
of this age are mined at Princeton and Nicola.
On the Pacific coast, the Eocene marine overlap of Oregon
and Washington extended into the estuary of the Frazer
river. Sediments were formed which are in part of marine
FIG. 1 80. MAP SHOWING THE NATURAL SUBDIVISIONS OF SOUTHERN
BRITISH COLUMBIA
After Daly.
and in part of freshwater origin. The thickness of these
deposits (Puget beds) must have been very great, for the
strata, evidently a mere remnant, exposed along the lower
part of the Frazer river are at least 3000 feet thick.
Farther north, sedimentary deposits of Tertiary age are of
little extent and not well understood. Undoubted marine
fossiliferous strata of Miocene age occur on Graham island,
and formations on Vancouver island are likewise thought to
belong to this epoch. Tertiary volcanics are of common
occurrence in Vancouver and Queen Charlotte islands and
northward into the islands of Alaska.
The great uplift of Pliocene times is thought to have
elevated the whole Cordilleran region of British Columbia to
heights differing greatly in different parts, but reaching
THE CENOZOIC ERA 337
maxima of 2000 to 4000 feet. By this elevation the rivers
were rejuvenated and a new cycle of erosion inaugurated
which has extended to the present time.
LIFE OF THE TERTIARY
With the close of the Cretaceous passed away for ever the
two dominant races of the Mesozoic, the great reptiles and
the ammonites. The belemnites dwindled to a meagre repre-
sentation in the Eocene; the cycads and conifers yielded to
the true flowering plants; and the familiar fish with thin,
flexible scales replaced in large part the more archaic fish of
the Mesozoic era. Of still greater interest and importance is
the advent and subsequent reign of the true mammals:
on this account the Tertiary is known, beyond all other
designations, as the Age of Mammals.
PLANTS. As already stated, the plant life of the Tertiary is
essentially that of the present day. While it is questionable
if any species of Tertiary plant is still in existence, many of
the extant genera lived in the Eocene and their number was
gradually increased as Tertiary time went on.
The Miocene witnessed a remarkable distribution of tropical
and sub-tropical plants into a latitude more polar than their
present habitat. Forests flourished as far north as Lat.
81° 45' in Greenland and Lat. 78° 56' in Spitzbergen.
Coal has been actually mined in Spitzbergen.
An interesting event of possible bearing on the development
of the mammals was the introduction of grasses in the Miocene.
INVERTEBRATES. The invertebrate life of the Tertiary is
essentially that of the present. A few species of the Eocene
are still in existence, and the number of living forms gradually
increased with the passage of Tertiary time. Marine inver-
tebrates are rare in Canada: the chief locality is Graham
island, the northern island of the Queen Charlotte group.
Freshwater molluscs belonging to a limited number of species
are common in certain layers of the Paskapoo and Estevan
formations of the plains. Species of Unio and Vivipams are
particularly abundant.
FISH. The general character of the fish fauna has already
338 ELEMENTARY GEOLOGY
been indicated. The Canadian Tertiary rocks have not yielded
many remains of fish: species of Amyzon have been found
in the Oligocene, Tranquille, and Similkameen beds of the
southern interior of British Columbia. Amia and Amiurus
occur in the Oligocene strata of the Cypress hills.
FIG. l8l. CANADIAN TERTIARY FISH
Amyzon brevipinnc from the Tertiary of British Columbia. About five-sixths natural size.
After Lambe.
REPTILES. Although the great reptiles of the Mesozoic era
have disappeared, essentially modern representatives of the
branch are well known throughout the Tertiary. The most
important feature of the reptilian life is the occurrence of
extremely large turtles, e.g. Trionyx, in the Oligocene beds
of the Cypress hills.
BIRDS. Birds probably existed throughout the Tertiary
in much greater number than the positive evidence of remains
would indicate. The life habits of birds are not favourable to
preservation. Only one skeleton has been found in Canada —
in the Puget Eocene beds of British Columbia. Tertiary birds
were toothless like those of the present.
TERTIARY MAMMALS
It has already been pointed out that mammals possibly
originated from theriodont reptiles in the Triassic. Through-
out the succeeding periods of the Mesozoic the evolution of
the new type was very slight ; as far as known, no mammals
existed except a few small forms belonging to the lowest
orders, in which the young are reproduced from eggs or are
born immature and carried in a brood pouch.
At the very base of the Tertiary appeared the first eutherian
or placental mammals, in which the young is nourished by the
mother's blood during the period of gestation and is born in a
THE CENOZOIC ERA 339
condition which permits independent existence. This class
of organism dominates the world to-day, and the history
of its development through Tertiary and Quaternary time
is not surpassed in interest by any other chapter of the
geological story.
Before proceeding to an account of the development of the
mammals in the Tertiary, it will be necessary to point out in
the briefest manner the basis on which existing eutherian
mammals are classified.
In all, nine orders of mammals are recognised: of these,
three are of much greater importance than the others from
the geological point of view.
The ungulates are the hoofed animals. Their teeth are
adapted to the eating of vegetable food. Although they are,
in some cases, provided with weapons of defence, their usual
mode of protection is by flight. Many sub-orders of ungulates,
of which some are entirely extinct, are known to science. Of
the present-day ungulates, the chief sub-orders are the
elephants, the odd-toed types, and the even-toed types.
The elephants, or Proboscidea, are characterised by having
five toes on each foot, by the peculiar teeth, and by the
possession of a trunk or proboscis, whence their name.
The odd-toed ungulates, or Perissodactyla, include the tapirs,
rhinoceroses, and horses, in all of which the axis of the foot
passes through the middle toe. In all forms, living and extinct,
there is a tendency, more or less marked, for the central toe,
particularly in the hind foot, to exceed the others in size
and importance.
The even-toed ungulates, or Artiodactyla, include the sheep,
cattle, deer, swine, etc., in which the axis of the foot passes
between the toes, which are usually two in number.
The carnivores are the predaceous, flesh-eating mammals,
in which the teeth are adapted to the seizing of prey and
the tearing of flesh. The lion, tiger, bear, dog, etc., are
typical carnivores.
The primates include man, gorillas, monkeys and lemurs.
All these animals have a superior intelligence and a more or
less erect posture.
The remaining six orders of mammals of less importance
from the present point of view are the insectivores (shrews
340 ELEMENTARY GEOLOGY
and moles), chiroptera (bats), edentates (anteaters, armadillos,
and sloths), cetaceans (whales, dolphins, porpoises), sirenians
(manatees and dugongs), zndrodents (mice, hares, beavers, etc.).
At the beginning of the Tertiary, in the Paleocene epoch,
there existed a number of small mammals not differing greatly
from the primitive types of the Mesozoic. With these there
appeared for the first time true eutherian mammals, of which
Phenacodus is the best known example. This creature is
worthy of especial attention as indicative of those general
characteristics, the modification and specialisation of which
have resulted in all the diverse races of placental mammals
now inhabiting the globe.
FIG. l82. PRIMITIVE BASAL EOCENE MAMMAL
Phenacodus primcevus. After Cope.
Phenacodus was a small creature about the size of a grey-
hound, with a skeleton of very general structure, i.e. the
various organs were not specialised for particular functions.
Its teeth were small and low-crowned, ill adapted for either
the crushing of grass or the tearing of flesh ; it had five fingers
and five toes, the extremities of which were armed with
structures which could not be called nails, claws, or hoofs;
its brain case was small and smooth, and the brain was
without the corrugations seen in all the higher mammals;
there were two bones in the lower j oints of all legs ; and the
bones of the two rows of the wrist and ankle were set opposite
one another, not alternating as in the higher mammals.
From such general and unspecialised animals as this there
developed throughout the Cenozoic the widely diversified
THE CENOZOIC ERA 341
animals which we know at the present time, and also a
number of races which have become extinct without leaving
any descendants.
Very soon, perhaps at the very beginning, the distinction
between ungulates and carnivores appeared, for some of the
Phenacodus-like creatures were slightly more ungulate than
carnivore-like, while others were slightly more like carnivores
in the structure of the teeth and toes. Before the close of the
Eocene the amount of differentiation was enormous. Different
races of ungulates evolved and became extinct; the differen-
tiation of even- toed and odd-toed ungulates was completed;
primitive carnivores appeared; insectivores, bats, lemurs,
monkeys, and even whales, had branched off from the parent
stem. We may go further and state that more intensive
evolution was effected, and that horses, rhinoceroses, tapirs,
pigs, etc., had been evolved. While it is doubtless true that
forms ancestral to these creatures had appeared, it must be
remembered that they were archaic forms and would scarcely
be called horses, tapirs, etc., in the modern acceptation of
these names.
The Oligocene and Miocene were characterised by the
survival of some of the Eocene types, by the development of
races which did not survive the epoch, and by the decidedly
more modern aspect of the creatures from which the present-
day mammals descended. Mammals existed which can with
certainty be ascribed to existing families and which can
confidently be regarded as the direct ancestors of living
forms. For the most part, however, evolution had not pro-
ceeded to the degree of producing modern genera. Undoubted
deer existed, but not the modern genus Cervus; horses were
present, but not the modern genus Equus, etc. On the other
hand, the numerous rhinoceroses were so like the existing
forms that they are ascribed to the genus Rhinoceros.
The Pliocene is characterised particularly by the develop-
ment of modern genera and the occurrence of some remarkable
edentates. Equus, Felis, Ursus, Castor, Cervus, and Bos are
among the Pliocene genera: that is to say, horses, cats, bears,
beavers, deer, and cattle existed. It is to be understood,
however, that none of the modern species arose until long
after the close of Pliocene time.
342
ELEMENTARY GEOLOGY
The above very general summary of the development of the
Tertiary mammals will be supplemented by a description of a
few of the important extinct groups and by an account of the
life history of some existing types of mammals.
EXTINCT GROUPS OF TERTIARY MAMMALS. The Blunt-toed
Ungulates. Very characteristic of Middle and Upper Eocene
time was a group of ungulates which in some cases reached
the dimensions of an elephant. They were heavily constructed
and retained in general the simplicity of structure shown by
Phenacodus. The primitive five toes were retained, but the
terminal bone of each digit was expanded into a blunt
structure which is very characteristic. Dinoceras and Uinta-
therium are well-known American examples.
FIG. 183
Palczotherium magnum, a primitive ungulate of the Upper Eocene. Greatly reduced.
After Cuvier.
The Titanotheres. Beginning in the Eocene and becoming
extinct in the Miocene is a remarkable group of odd-toed
ungulates known as titanotheres, some of which rivalled the
elephant in size, and are to be included among the more
important Miocene fossils. These great creatures are not
blunt- toed like Dinoceras, but the primitive five toes have
become reduced to four in the front foot and to three in
the hind foot. The teeth are more specialised, with a charac-
teristic W- shaped cutting edge on the outside of the molars.
Titanotherium from the Miocene of Dakota is the best
known example.
The Palczotheres. These animals were very important in
the Upper Eocene: they belong to the odd- toed ungulates,
and are regarded as ancestral to both horses and rhinoceroses.
THE CENOZOIC ERA
343
The dentition resembles that of the titanotheres, and the toes
have been reduced to three on both front and hind foot.
The Elotheres. This group of pig-like animals was very
abundant in the Miocene. The feet show the even-toed struc-
ture and a high degree of specialisation in that they are
already reduced to two on each foot.
The Oreodonts. Under this name is included a group of
slender, even- toed ungulates of the Miocene: they have four
functional toes on each foot, and a very long tail — Oreodon,
Agriochcerus.
The Creodonts. This name is given to the most primitive
type of carnivorous mammal, which began in the Lower
Eocene and survived into the Middle Miocene. The earliest
creodonts are scarcely to be distinguished from the contem-
porary ungulates, but the later forms are most distinctly carni-
vorous and pass insensibly into the true carnivores. Mesonyx
and Hycenodon from the Eocene of
America are the best examples.
THE DEVELOPMENT OF TYPICAL
RACES OF MODERN MAMMALS. The
Horse. Our knowledge of the
development of mammalian life in
the Tertiary is best understood and
is best illustrated in the case of
those creatures which culminated
in the modern horse.
Early in the Eocene, not long
after the reign of the five- toed
Phenacodus, appeared a small
animal, Hyracotherium, not much
more than two feet in length. This
little creature had very simple teeth,
but more specialised than those of FIG. 184. THE EVOLUTION OF
Phenacodus, and the five toes had THE HORSE
, , j , r ,1 f , («) Protorohippus, Eocene; (b) Om-
been reduced to four in the front kippus, Eocene; (c) Mesohippus, 011-
foot and three in the hind foot,
with a splint representing the fifth
toe. The animal is not a horse, but
it is distinctly an odd-toed ungulate and is confidently
believed to be ancestral to the present-day horse.
ocene ;
; (/) Equus,
The Evolution
344
ELEMENTARY GEOLOGY
Before the close of the Eocene appeared Protorohippus,
a palaeothere, in which the splints have gone, the teeth
become deeper, and the small bone of the lower leg some-
what reduced.
Mesohippus, also a palaeothere, is characteristic of Oligocene
time: it is larger and has three functional toes on each foot
with a splint on the front foot only.
In the Miocene the typical animal of this line of descent had
become so horse-like that it is included in the family Equidcz.
Protohippus is larger than its predecessors, the teeth are much
THE EVOLUTION OF THE HORSE.
FIG. 185. THE EVOLUTION OF THE HORSE
After Osborne.
deeper, the smaller bone of the lower limb is still fuither
reduced, and the two outer toes are not functional, i.e. they
do not touch the ground.
Before the close of the Pliocene the genus Equus had evolved.
Only one toe is functional, and the two outer toes are reduced
to mere splints; the teeth are deep with complicated folds of
enamel; and the small bone of the lower limb has dwindled
and fused with the larger bone to make one rigid element.
The above example illustrates the transition of a small
marsh-dwelling creature, living upon soft vegetation, to an
animal capable of rapid motion on the open plains and of
sustaining life by eating hard and dry grasses. Naturally, the
THE CENOZOIC ERA
345
changes are best seen in those organs which come in contact
with external objects — the teeth and feet.
The Elephant. In this case the ancestral creatures did not
wander out on the plains and develop habits of flight, and in
consequence the toes and the bones of the lower joint of the
limbs have remained primitive to
the present day. On the other hand,
the whole effect of specialisation and
adaptation is shown in the head
structures — the teeth, tusks and
trunk. As far back as the Middle
Eocene appeared an animal, Mceri-
therium, which shows primitive
elephantine characteristics. It had
a short flexible proboscis and the
outer incisors in the upper jaw were
extended into short tusks, while the
corresponding teeth of the lower jaw
were directed outwards.
Between this simple form and the
modern elephant many transitions
are known. At first the chin elon-
gates and results in forms with four
tusks ; later it retracts and the tusks
of the upper jaw become very large
coincident with an increase in the
size of the trunk. There is a steady
progression in the adaptation of the
teeth, with a tendency towards a
greater number of transverse rows
of cusps. Finally, when the rows of cusps have become very
narrow, the space between them is filled in with a secondary
deposit, the cement.
Four-tusked proboscideans were common in the Miocene
and also a remarkable form, Dinotherium, in which the lower
jaw was curved downwards and a pair of downwardly- directed
tusks inserted in its extremity. Mastodon, a large elephant-
like creature, ranged from the Miocene almost into the Recent:
it differs from the elephant in that the teeth show fewer
rows of cusps, usually only three or four, and there is
FIG. 1 86. THE EVOLUTION
OF THE ELEPHANT FAMILY
DURING THE TERTIARY ,
(a) Elephas, Pleistocene; (b)*Mam-
mut, Pleistocene; (c) Tetrabelodon,
Miocene; (d) Palceomastodon, Oligo-
cene; (e) Mceritherium, Eocene.
After R. S. Lull, from "Guide to
Peabody Museum, Yale University.''
34^
ELEMENTARY GEOLOGY
no cement. Elephas itself is represented by extinct species
in the Pliocene.
The Carnivores. The record of carnivorous mammals is
not so complete as that of the ungulates, nevertheless there
is evidence of the appearance of true carnivores in the Upper
Eocene. These early forms are remarkably dog-like, and later
forms show transitional stages between the various groups of
living carnivores. The most remarkable fossil carnivores are
the NimravidcB, a family of ferocious, tiger-like creatures of
great size. Numravus and Machcerodus were armed with
enormous tusk-like canine teeth: the former belongs to the
__ _ ____ " ' Miocene, and the latter
extends from the Miocene
into the Post-pliocene.
The Primates. This high
group of mammals is thought
to have developed from
insectivores. The lower
forms (lemurs) are known
from Eocene deposits of both
Europe and America, but
thpv arp nnt knnwn in tViACA
^J ar6 l KUOWn in tnCSC
continents after the begin-
ning of the Miocene. At present they occur only in Madagascar
and in parts of Africa and southern Asia.
The true apes appear in the Middle Miocene. The best
known form is Mesopithecus from Lower Pliocene strata
near Athens.
FIG. 187. MIOCENE APE
Mesopithecus pentelicus, from the Upper Miocene
of Pikermi, near Athens. After Gaudry.
CHAPTER XVII
THE QUATERNARY PERIOD— THE PLEISTOCENE EPOCH
THE Pleistocene, or "most recent" time, comprises the latter
part of the Cenozoic, extending from the close of the Pliocene
to the Recent. The period term, Quaternary, a remnant of
an early classification, is practically synonymous.
The beginning of this time is well marked in many northern
and far southern regions by the on-coming of the Ice Age;
but beyond the limits of glaciation the division between the
Pliocene and the Pleistocene is much less certain. The end of
the Pleistocene is quite indefinite since no important change
of conditions separates it from recent times. In early American
works on geology the Quaternary is divided into three periods
as follows:
Recent period. Elevation, existing con-
ditions, with species of animals still living.
Champlain period. Depression of the land
Quaternary <
and invasion of the sea.
Glacial period. Elevation and great ice
sheets.
THE GLACIAL PERIOD l
In the earlier days of the science, the Glacial period was
thought of as a unit and was considered as of comparatively
short duration. Later work has shown that the Glacial period
was really of enormous length as compared with the other
two and was broken by warm intervals, Interglacial periods,
lasting many thousands of years, each probably of much more
1 The use of the word "period" for these divisions is sanctioned by
custom; they are not periods in the stricter sense of the term.
347
348 ELEMENTARY GEOLOGY
importance than the Champlain and Recent periods combined.
The most complete classification of the formations of the
Glacial period has been made in Iowa and adjacent states,
where the deposits of the different ice advances and the
interglacial beds are best displayed: it is as follows:
Post-glacial time.
Wisconsin ice advance.
Peorian interglacial stage,
lowan ice advance.
Sangamon interglacial stage.
Illinoian ice advance.
Yarmouth interglacial stage.
Kansan ice advance.
Aftonian interglacial stage.
Nebraskan (Pre-Kansan or Albertan) ice advance.
Conditions during the Pleistocene in North America were
very unstable, with Arctic climates interchanging with tem-
perate climates. It is probable that these changes affected the
whole continent and very likely the whole world; although
in what are now warm temperate and tropical regions the
cooling down was not great enough to produce ice sheets
except on high mountains.
The succession of events recorded in the central United
States no doubt extended into Canada also, but later ice
advances over a given region usually destroy the evidence of
earlier ones, so that only the effects of the last, or Wisconsin,
ice advance are widely shown. One great interglacial interval
with a warmer climate than the present is splendidly dis-
played at Toronto and also in the Moose River region, and
evidences of interglacial times occur in Manitoba, Alberta,
and British Columbia.
EXTENT OF GLACIATION IN NORTH AMERICA
So far as known, glaciation on our continent began in the
Rocky Mountain or Cordilleran region, where small mountain
glaciers expanded as the climate grew colder at the end of
the Pliocene and coalesced into great valley glaciers, bury-
ing much of British Columbia and the mountainous part
THE QUATERNARY PERIOD 349
of Alberta, except the higher peaks, which projected as
"nunataks" abova the fields of snow.
Next, as shown by J. B. Tyrrell, ice accumulated west of
Hudson bay in the Keewatin region. Here the ice formed on
l-Centre of Cordilleron Sheet
2- •' « Keewqtin »'
" •« Labrador »•
4- *» .. Greenland
FIG. 1 88. GLACIAL MAP OF NORTH AMERICA
low ground, averaging not more than 1500 feet above the
sea at present, and expanded to a vast sheet which reached
the Rockies on the south-west and advanced as far south-east
as Cincinnati in Lat. 38° N. ! It seems also to have occupied
much of the bed of Hudson bay. It carried Pre-cambrian
350 ELEMENTARY GEOLOGY
boulders 800 miles from the Keewatin region to the foothills
of the Rockies, leaving them at elevations 2000 or 3000 feet
above their starting-point. An uphill motion of ice sheets
may be accounted for by the great thickness of ice at the
centre, so that the surface has an opposite gradient. It is the
slope of the upper and not of the under surface of the sheet
which determines the motion. Similar upgrade movements of
ice sheets are known in other countries, e.g. in Sweden,
where boulders were transported across the mountains on
the Norwegian border.
Mr. Tyrrell has shown that at one time in the Pleistocene a
comparatively small glacial centre existed in north-western
Ontario, forming the Patrician ice sheet, but this was
merged in the larger neighbouring sheets at the time of
their greatest extension.
The Labradorean ice sheet began east of James bay in Lat.
52° N., as shown by Low, and covered nearly all of eastern
Canada and a considerable part of the northern states. It was
this ice sheet which covered southern Ontario ; and it appears
to have passed right over the Adirondack mountains, which
reach a height of 5000 feet, so that its thickness to the north
may have been 10,000 or even 15,000 feet.
The Greenland ice sheet may be mentioned to complete the
series. When this great island was first glaciated is not known,
but it is still in the Ice Age, though a fringe of coast is free
from snow in the summer.
The whole area covered with ice at one time or another was
about 4,000,000 square miles, its southern edge running
roughly a degree south of the boundary of British Columbia,
then following the Missouri south-east to the Mississippi, then
the Ohio north-east, and finally bending a little south of east
and ending at New York City.
All of Canada except the higher parts of the Cordillera, the
northern part of the Yukon Territory, the Torngat highlands
in north-eastern Labrador, and the Shickshock mountains of
Quebec seems to have been covered with ice at some time
during the Glacial period. These regions, still among the
coldest in America, seem to have been left uncovered because
of their small snowfall; for cold alone, without moisture for
precipitation as snow, will not produce an ice sheet.
THE QUATERNARY PERIOD 351
CONDITIONS DURING THE GLACIAL PERIOD
The climate during the Cenozoic underwent important
variations, but for the greater part was mild even in the far
north, as shown by remains of luxuriant forests in Spitz-
bergen and Greenland; and by the trees of Dunvegan in
northern Alberta, which remind one of the southern states at
present. During the Pliocene, however, the temperature fell,
and while the gold-bearing gravels of the Klondike placers
FIG. 189. INTERGLACIAL BEDS (BETWEEN PARALLEL DARK LINES)
Don Valley Brickyard, Toronto, Ontario.
were being deposited in the Yukon Territory the climate
seems to have been about as cold as at present, with a growth
of birch and spruce trees and a splendid fauna, including
elephants, horses, bears, deer, and bison.
The slowly on-coming ice blotted out all life as it advanced
until Canada was glacier-covered and blizzards swept over
the white plains in every month in the year. The only
existing parallel to these conditions is to be seen in Greenland
or the Antarctic continent.
I
Bf
Bl
H „
W J3
PQ *"
o °
t
SI1
Q •»
W en
THE QUATERNARY PERIOD
353
INTERGLACIAL PERIODS
As shown on a former page, evidence of several interglacial
periods is found in the United States and of at least one
important one in Canada. In the earliest interglacial time,
the Aftonian of Iowa, animal life included "ground sloths "
like Mylodon and Megalonyx, camels, sabre-toothed tigers,
as well as bears, horses, and elephants. The trees of the time
seem to have been not very different from those of the present.
The best preserved
interglacial beds of
Canada, named the
Toronto formation, may
be of the same age or
may correspond to the
Yarmouth or Sangamon
stage. The Toronto
formation has provided
much the largest number
of fossils, both of plants
and animals, yet found
between two ice ad-
vances in the American
Pleistocene. It includes
freshwater shell fish of
modern species; many
of the clam shells now
living in more southerly
waters; seventy-two
FIG. IQI
Acer pleistocenicum, an extinct maple from the Inter-
F • 11 i glacial beds, Don Valley. Toronto.
species of insects, all but
two extinct; remains of fish, and of elephants, bison, deer,
bears, and other mammals.
In certain beds of clay in the lower part of the formation
there are many tree trunks and branches, as well as beauti-
fully preserved leaves. More than thirty trees have been
recognised, such as oak, maple, hickory, basswood, wild plum,
red cedar, which can still grow in the region ; and also some,
like the pawpaw and osage orange, which belong to a region
much farther south. Botanists believe that the climate was
several degrees warmer than at present, like that of Ohio or
z
354
ELEMENTARY GEOLOGY
Pennsylvania. There is evidence to show that the Toronto
interglacial interval lasted for 75,000 or 100,000 years.
The beds of lignite between two boulder clays near Moose
river, 350 miles north, which include large trees and indicate
a long and mild interglacial stage, were probably formed at
the same time, proving that the Labrador ice sheet had
completely vanished.
I
i
FIG. 192. EXTINCT BEETLES
From Interglacial beds, Scarboro heights, Toronto.
There are interglacial beds at Rolling river in Manitoba,
Rosebud creek and Belly river in Alberta, and at some points
in British Columbia; but it is uncertain whether they are of
the same age as the beds described from Ontario.
THE WITHDRAWAL OF THE ICE SHEETS AND THE
FORMATION OF GLACIAL LAKES
After each glacial stage had reached its climax the warming
up of the climate caused the ice sheets to retreat slowly in
the opposite direction from their advance. The centres of the
Keewatin and Labrador ice sheets are so placed that the most
important drainage systems of Canada would be blocked by
their advance and set free gradually on their retreat. As a
THE QUATERNARY PERIOD 355
consequence, the waters of these river basins must have been
ponded back into great lakes during the on-coming of the ice,
and similar lakes must have formed in front of the ice as it
withdrew. The series of glacial lakes following up the Wis-
consin ice sheets when they began to wane has been carefully
studied in some places, and the lakes thus formed have left
important effects in the central provinces of Canada.
The fertile soils of Edmonton and Calgary seem to have
been formed by the silt of great glacial lakes, though their
boundaries and outlets have not yet been worked out. Lake
FIG. 193. SKETCH MAP OF POST-GLACIAL LAKES
Agassiz occupied parts of Saskatchewan, Manitoba, western
Ontario, North Dakota, and Minnesota, and probably covered
more than 100,000 square miles — more than three times the
area of Lake Superior. As the present outlet for the southern
prairie waters through Nelson river to Hudson bay was ice-
covered, the great basin spilled southwards by the Red River
valley and reached the Mississippi, which must have been
greatly swollen at that time. The old beaches of Lake Agassiz
are plainly to be seen, and the finer deposits off shore make
some of the flattest and most fertile prairies, as near Winnipeg.
The final separation of the Keewatin and Labrador or Patricia
ice sheets permitted the waters to flow north-east, but
remnants of Lake Agassiz still remain, forming Lake Winnipeg
and others of the Manitoba lakes.
356 ELEMENTARY GEOLOGY
While Lake Agassiz still existed the basins of the Great
Lakes began to be set free by the thawing of lobes of the
Labrador ice sheet, and at length those of Superior, Michigan,
and Huron united to form Lake Algonquin, almost as large
as Agassiz and very much deeper. It had several outlets at
different times, first probably past Chicago into the Missis-
sippi, then over Niagara Falls, then by the Trent valley, and
finally once more over Niagara Falls. For most of its existence
the outlet was into Lake Iroquois, which occupied the Ontario
basin and drained past Rome, N.Y., into the Hudson.
The shore cliffs and beaches of Lakes Algonquin and Iroquois
are almost as perfect as those of the present lakes, but usually
stand much higher up and are no longer horizontal. They
have undergone "differential elevation," and rise as one
advances in a direction of N. 20° E. The land in that quarter
sank beneath its immense load of ice and then rose again as
the load was removed by the melting of the ice sheets,
deforming the once horizontal beaches.
Another glacial lake, called Lake Ojibway, but less perfectly
known, deposited the great belt of clay north of the Hudson
Bay watershed in Ontario and Quebec.
These vanished lakes have left us fertile soils and well-
drained sites for railroads and cities, as well as supplies of
sand and gravel useful for many purposes.
THE MARINE EPISODE OR CHAMPLAIN PERIOD
It has just been shown that the northern part of the con-
tinent was depressed by the sheets of ice which gathered upon
it in the glacial periods. As the ice withdrew, all the land
below a certain level was flooded by the sea in what has been
called the Champlain period, because its effects are well shown
near Lake Champlain. Marine beaches are found from New
York northwards, ascending as one advances and reaching a
maximum of 690 feet above present sea level at Kingsmere in
the Ottawa valley. Marine beaches are found on Mount
Royal at 620 feet, and occur hundreds of feet above the sea
along the lower St. Lawrence and on the shores of Labrador.
THE QUATERNARY PERIOD 357
To the north-east in Labrador they grow lower, reaching only
225 feet at the most northerly point studied. Around Hudson
bay raised beaches are found up to 450 feet.
In many of the beach deposits there are sea shells belonging
to species now living in nearby waters, and remains of whales,
porpoises, and seals have been found in eastern Ontario. Sea
shells are found as far west as Brockville, but not around the
shores of Lake Ontario, though the basin must have been
far below sea level. Probably the Niagara river kept the
waters fresh.
Marine deposits are found up to about 350 feet along the
shores of British Columbia also, and shell beds occur in
Stanley Park, Vancouver, and at Nanaimo, as well as else-
where in the province.
With the waning and final disappearance of the ice sheets,
the depressed portions of the country rose and slowly reached
their present level.
PHYSIOGRAPHIC EFFECT OF THE GLACIAL
PERIOD
At the end of the Pliocene it is probable that Canada was
deeply mantled with the products of millions of years of
weathering ; that most of the rivers had mature valleys ; and
that lakes were infrequent. After the final retreat of the
Wisconsin ice sheet the country was left in a totally different
condition, the central areas of glaciation having been scoured
to the bare solid rock, and the debris having been spread as
boulder clay or piled as crescent-shaped moraines over the
region to the south. As a result, basins were excavated in the
rock or made by the dumping of glacial debris across valleys.
In this way innumerable lakes were formed, so that Canada
probably has as many lakes as all the rest of the world; and
the drainage was completely disorganised, rivers flowing at
haphazard wherever the slope of the drift deposits permitted.
Thus it is that Canada presents physiographically so very
youthful an aspect, almost every river having lakes threaded
on its course and tumbling at one point or another over rocky
obstructions causing rapids or falls. The youthful condition
358
ELEMENTARY GEOLOGY
of the drainage provides lakes great and small for navigation,
and waterfalls of all dimensions for power.
The rock flour of the wide-spread sheets of boulder clay is
generally rich in lime, potash, and phosphorus, the essential
mineral ingredients of a good soil, unlike the profoundly
leached residual soils south of the glaciated region. On the
other hand, the central areas of glaciation are largely bare
rock and useless except for their mineral contents.
FIG. 194
Restoration of the mastodon, Mammut americanum, by G. M. Gleason from a painting in the
National Museum, Washington.
THE PLEISTOCENE IN OTHER REGIONS
South of the glaciated area just described, beds of sand and
gravel were formed and rock weathering continued, but the
results are much less marked. In South America, glaciers
descended 1000 metres or more below the present level of snow
on the Andes, and Patagonia was covered by an ice sheet.
Two ice advances with an interglacial period have been found.
Next to North America Europe was the continent most
affected by the Glacial period, and ice covered about 2,000,000
THE QUATERNARY PERIOD 359
square miles, reaching Lat. 52° N. on low land, while the
Alpine glaciers descended far below the present level. Euro-
pean geologists describe four great ice advances in the Alps,
separated by three interglacial periods. Just how these
subdivisions correspond with those recognised in America is
not certain.
It is interesting to find that Siberia, the coldest part of the
earth's surface, like our Klondike region, was not glaciated on
a large scale, though the mountain glaciers of the Himalayas
to the south reached thousands of feet lower down than at
present. In Africa and Australia the effects of the Glacial
period are found only on the highest mountains.
THE LIFE OF THE PLEISTOCENE
Mammals seem to have reached their highest point in
variety, numbers, and size in the Pleistocene. In North
America, ground sloths
and elephants (mam-
moths and mastodons)
survived all the ice
advances, which might
have been expected to
destroy such large,
plant-feeding animals,
and then perished by
some unknown cause
as the climate grew
milder. Horses, camels,
tapirs, and the sabre-
toothed tiger perished
earlier.
In Europe many
animals now thought
f Af ' Ik FIG'
OI aS African, SUCn as The g,.eat ground sloth of the Pleistocene, Megatherium
americanum. About^eightieth natural size.
the mammoth (ele-
phant), woolly rhino-
ceros, hippopotamus, and lion, survived until the middle of
the Glacial period, and even reached England, then joined
by land to the Continent.
360
ELEMENTARY GEOLOGY
In South America the gigantic ground sloths, Mylodon,
Megatherium, etc., which pulled down or dug up small trees
to feed on their foliage, passed away toward the end of the
Pleistocene, leaving only the small, present-day sloth hanging
beneath the branches in Brazilian forests as a survivor, and
the huge Glyptodon with a shell of bony plates is succeeded
by the little burrowing armadillo.
In Australia there were giant marsupials, e.g. Diprotodon,
which have left only diminutive descendants; and in New
FIG. 196. PLEISTOCENE CARNIVORE
Machcerodus neogceus, from the Pleistocene of Argentina. Reduced. After Burmeister.
Zealand and Madagascar there were huge running birds
without the power of flight, Dinornis and Mpyornis, larger
than the ostrich, which have left no descendants in the latter
island, and only the little apteryx in New Zealand.
Africa, and to a less extent Asia, are the only continents
which have preserved their mammal fauna to a large degree,
and these two continents were comparatively little affected
by glacial action.
Plants and the lower animals, with the exception of insects,
seem to have undergone little change during the Pleistocene.
MAN'S APPEARANCE IN GEOLOGY
The most important of the mammals — man — remains to be
considered. That he is closely related to the higher apes is
shown by the fact that almost every human bone and muscle
THE QUATERNARY PERIOD 361
has its counterpart in a gorilla or chimpanzee, the chief
differences being the adaptation of the hind limbs to walk-
ing upright, the development of the thumb and fingers of
the hand, and the much larger brain. From these facts
evolutionists conclude that man and the higher apes have
descended from a common ancestry.
Just where man originated is not certain, but the pro-
babilities point to southern Asia as the place and the early
FIG. 197. PLEISTOCENE MARSUPIAL
Diprotodon australis, about one-fiftieth natural size. After Owen.
part of the Pleistocene as the time. At Trinil in Java about
the beginning of the Pleistocene there lived, along with a
number of other extinct animals, a somewhat man-like
creature which has been called Pithecanthropus erectus. The
remains include the greater part of the skull, a thigh bone
and two teeth, and belonged to a creature which walked
upright, had human-looking teeth, and a brain more than
half as large as that of the average modern man and far
larger than that of any ape. Pithecanthropus seems, there-
fore, to have been an intermediate form, as the name suggests,
an ape-man.
Throughout the Cenozoic the mammals had been steadily
362 ELEMENTARY GEOLOGY
increasing the size of their brains, and the climax of this
development of brains was reached in man himself.
There is no certain evidence of men in America before the
end of the Ice Age, so that it is necessary to go to the Old
World for information as to the first men. The earliest
supposed proofs of their existence in Europe are the eoliths,
rudely chipped bits of flint found in deposits belonging to the
early Pleistocene or the end of the Pliocene; but some
authorities doubt the human origin of these imperfect knives
or scrapers and think them due to accidental fractures.
The first undoubted tools occur, apparently, near the
beginning of the last interglacial time, and the finding of a
few fragmentary jaws and skulls make it certain that man
existed. The climate seems to have been somewhat warmer
than at present, and the animals found associated with man
suggest Africa, which was then connected directly with
Europe, and include elephants, the rhinoceros, the hippo-
potamus, and the sabre-toothed tiger or lion.
Later in this interglacial period the climate grew colder and
man began to take refuge in caverns instead of living in the
open. Complete skeletons show that the men of the time had
slightly bent knees, a receding chin, and a massive bony ridge
at the eyebrows, with a very retreating forehead above. They
could not have been prepossessing according to our standards,
though their brains were nearly equal in size to those of
modern men, and they had already made man's most funda-
mental discovery, the use of fire.
From the beautifully chipped flint arrowheads, knives and
scrapers which they made, these men have been called
paleolithic (ancient stone) ; and they seem to have been an
artistic people, since they have left many sketches or even
coloured pictures of the animals which they hunted. Their
prey included several creatures adapted to endure a cold
climate, such as the hairy mammoth and rhinoceros, the bison
and, at the on-coming of the last ice advance, the musk ox
and reindeer.
The Palaeolithic stage was a long one ; but with the recession
of the last ice sheets a new race comes in, more like modern
European man, and better armed, since it had learned to
grind into shape stone axes and other tools, which were much
THE QUATERNARY PERIOD 363
more efficient than the brittle flint tools of the earlier time.
These men have been called neolithic (new stone) ; still later
Europeans acquired the use of bronze and other metals, as
shown by the earliest historic records, and one enters upon the
field of ancient history rather than geology.
Our North American Indians, before the coming of the
white man, were still in the stone age, and combined the use
of chipped arrowheads, etc., like Palaeolithic tools, with that
of ground and polished axes like those of Neolithic times.
To a slight extent they used native copper also, corresponding
to the age of bronze.
The earliest hint of man in Canada is the reported finding of
stone tools along with bones of the caribou at the bottom of
the Iroquois gravel bar in West Toronto; which takes us
back thousands of years to the time when the last ice sheet
still lingered in the Thousand Island region. Unfortunately
the evidence is meagre and the find was not investigated by
any trained scientific observer.
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